I decided to put this review up as a few reviewers have issues with the accuracy of the altimeter readings, and may not understand the limitations of these watches:Design======The PRG270 is smaller than some of the older Protrek models, due to the smaller sensor, and they have moved the sensor location from the 10 o'clock to the 9 o'clock position. The triple sensor makes these watches sometimes called ABC watches as they have Altitude, Barometer & Compass readouts. The smaller design makes it easier to wear everyday, however the face is still relatively busy, with the case having front raised sections (at the 12, 3, 6 & 9) with indents. The sensor at the 9 o'clock position sits higher than the raised section at the 3 o'clock position. The crystal is recessed nicely as usual on Casio G-Shocks and Protreks.I wish the design could look more like the PRW3000, which is cleaner and more stylish IMHO Casio Men's PRW-3000-1ACR Protrek Digital Display Japanese Quartz Black Watch, but is also 3 times more expensive. The display is similar to the other Protreks, divided into three sections. The top section has a dotmatrix display and can show the date, or altitude/barometric graphs, the middle section is the time, and the lower section is the seconds.The watch is light, mine weighs about 67 grams (2.36 ounces), and has 10Bar water resistance, which means it is ok in a rain shower, or shallow swim, but it wouldn't be ok with a scuba dive. I have only had this watch in the rain, and it functions fine.One issue with the PRG270 is the strap uses a 18mm spring lug, so if you wanted to put a wider Nato/Zulu strap, you'd need an adapter.Features=======- EL backlight, this is nice and bright, and the EL button is still on the front, they have moved the adjust button on older Protreks from the front to the 10 o'clock position. You can still set this for Automatic, and set it for 1 or 3 second display.- Date display - on the Time display, you can change date to Day&Date, or Month&Date, or Barometric Graph only (no date).- Setting time - this is a breeze. when you get the watch is preset to Tokyo time. Changing the Time zone to your location, and checking if Daylight Saving Time (DST) applies, and voila - the time is set and easy to change if you travel. The secondary timezone is set by picking various preset cities. I have not had any issue with the time accuracy so far.- Stopwatch/Countdown TImer (24 hours max)/Alarm - All standard, but the alarm lets you have 5 individual alarms, and the alarm is louder and longer than my Suunto Core watches.- Sunrise/Sunset - this is also a breeze to set. The PRG270 lets you input the longitude and latitude of your location for accurate sunrise/sunset times. Compared with my Suunto Core watches which only lets me choose nearest cities.- Power save - I have set this to on, and the watch will display will go off overnight, or after a period of unuse to conserve battery. You can wake it up by pressing any button.Altimeter/Barometer (This is from my previous reply comment to a review on the altimeter readings)=======All altimeter watches without GPS embedded will calculate the estimate of altitude by changes in air (barometric) pressure.Air pressure can change due to many things, like change in elevation, change in weather, your physical location and wind. So for example, if you get a low pressure system coming through over night, while you leave your watch on the table, it could appear that you have ascended a few hundred feet in your sleep. Similarly, if you take the watch on a commercial airplane, it will not give you a reading on the actual altitude, but a lower altitude, based on the pressure within the cabin. If you fly in an unpressurized aircraft, it will give you a more accurate altitude reading. I have taken a Suunto Core with me when I've been in a few prop aircraft, and used it as a secondary altimeter in skydiving, and it has been fairly accurate after calibration. I'll take the Casio up next time and see how it goes.Also, I have found that the altimeter and barometer readings tend to vary with temperature, and gives marginally more accurate readings off the wrist especially if I have been hiking and my wrist is warm.I also have a few Suunto Core watches, and the Suunto Core is quite clever in the way it calculates the altitude. If you leave it in altitude logging, it will gain elevation as you physically climb up, as the barometric pressure changes faster than it does when the weather changes, so it realises you are climbing. But once you stop climbing for a while, it realises this and any slight air pressure changes it takes as weather change, and not altitude gain or loss. The Casio doesn't have this feature.For accurate altimeter readings you still need to calibrate your altimeter watch to your reference altitude on a fairly regular basis. I do this when I want to log altitudes before a hike/climb. An easy way to do this is to check Google Earth which gives accurate altitude readings when you put your location. You can then calibrate the barometric pressure from your local meteorology service (I take mine from their website on the day I calibrate).If kept properly calibrated during a day that has fairly stable weather, they should prove to be very accurate overall. In varying weather conditions, you will see some variation. Again, it's essential to know the reference altitude to get back on track.Still, this can vary, and the altimeter watch is not a scientific instrument, but only designed to give you an estimate on current altitude. For example, on a recent trek to Mt Everest Base Camp, I ran a few loggers, including a barometric altimeter, and on the return trek later in the day because I was exhausted, I didn't recalibrate the altimeter at the known peak height, the altimeter log showed an altitude difference of about 10 metres (see here imgur.com/8XrW0iD)So if you are after an altimeter watch for accurate altitude readings at specific location, without daily calibration, the Casio PRG 270 it is not the right tool for you.The accuracy of the altimeter when properly calibrated is pretty close when I've compared it with my Suunto Core watches, Garmin handheld GPSs and altitude markers on trails. I usually the watch strapped to my backpack strap when hiking, so it doesn't get thrown out by my body temperature.Also, I haven't checked how fast the altimeter updates. It seems ok for hiking, but I haven't taken readings and monitored it while bike riding for example. The newer V3 Sensor has reduced the time required to measure altitude from 5 seconds previously to 1 second now, and the altitude measurement unit has been improved from five metres to one metre.The temperature reading in the barometer was pretty accurate, but I've noticed it can get wierd with rapid changes in temperature. For example, if you have left the watch by the window to solar charge, the temperature will be wrong for about half an hour until the watch and sensor cools down, and you get a more accurate measurement. You should only calibrate the temperature when the watch has cooled to normal temperature, and I have done this with a high accuracy thermometer. The temperature reading it gives includes 1 decimal place. In my Suunto Core, it only displayed the nearest degree, but after calibration, both Suunto watches and the PRG270 are pretty accurate on temperature off wrist.Altimeter logs - the watch has enough memory to store 30 logs, and 14 trek logs, but I think the Suunto is better here as it can record more.Compass========As with all electronic compasses, it will get interferences from other magnetic sources, and may not be accurate on boats, planes, trains, or even in some buildings where the ferroconcrete magnetism causes inaccurate readings. That said, I have had good experiences with the compass, in those conditions. The magnetic compass can be set for magnetic declination, and you can still display the time in Compass mode. The top section can be set to display the bearing (0°-360°) or the direction (N,S,E,W, etc).You have to have the watch level with the ground to get an accurate compass reading, and it is easy to calibrate by holding the adjust button down. You should only calibrate when way from other magnetic sources. I do this when I'm starting a hike, away from the car, but always carry a real compass and maps if going out bush.If you leave it in compass mode it will stop the compass to save battery.Summary=======Overall, for the price, this is a very good triple sensor watch that because of the smaller size from previous Protreks you can use for everyday wear. If you understand the limitations of ABC watches (they are not intended as precision instruments), this is a great first ABC watch.