I am using it to train and it is really useful.
The only thing that is not good is the buttons are very sensible and can be pressed with only the only movement of the hand

After reading the other reviews I was skeptical about the functionality of this watch but my concerns were unfounded. I bought this watch for two reasons, to have the reliability of a basic Suunto altimeter and for the Heartrate monitor.

All of the functions of the watch have worked well while training on my bike(s) and while I can see where a reviewer had the watch "jump" from screen to screen, I find that as long as it isn't touching my glove, I have no problems at all.

For the price, this is a great buy. Yes, you can look for more altimeter features but you pay for them. I am happy with this buy - in fact, after having my first watch stolen, I replaced it with the exact same model.

this is my 2nd X3... The older type straps broke on the 1st one and is being used as hiking watch attached to the pack.. if you want to measure HR, HR ave and ascent/descent this is the cheapest tool to do it. I use mine for mtb training - brilliant!

I really like this watch. First, it does a great job at the basic task of telling time. The heart rate monitor is cool too and offers some unique display feature to make it more readable in the middle of work outs. And the Ascent/Descent thing has made skiing that much more fun this year. Great buy for anyone thinking about it.

My biggest complaint about the X3HR is the function buttons. Every time I would look down at the watch the screen would have changed. Unintentional function changes would happen all of the time. I found myself always having to scroll back to the time, or accidentally activating the stopwatch, altimeter log, etc.

Plain and simple; I hate having stuff on my wrists. However, this watch converted me. super easy to use features have made me a watch wearer. Altimeter is very accurate. Like all you do have to set it before you leave, however it stays within 15 feet for the rest of that day. Which if you've owned other watches you'll know that is not to shabby.
The heart rate monitor works well also. The strap is as comfortable as can be expected. I'm a sweaty guy and have had no problems with the strap taking on moisture. All around this is a great buy.