1+ what as3753 said above.
It is a no-frills computer, but since I don't dive nitrox I'm very pleased with it. There are pro's and con's to any "one button" computer. The pro's are generally simple use, the cons are generally more difficult setup because you have a lot of cycling through settings to do.... but that only took a few minutes. And you only have to do it once (except for using "guage" mode as a techincal bottom timer as mentioned above... it was not really designed to do that well, but will as as3753 said, with some hassle).
Underwater it works great, the single button allow you to scroll through the main displays quickly. Mine has been very reliable. I had to change the battery at just short of one year of use. The battery is easy enough to change, and is available from most stores that have a camera department (it uses a fairly common camera-type battery).
If you think nitrox is in your future, look elsewhere. For recreational, non-deco air dives, it works great.
Best wishes.