I've logged about 13 dives on my Vyper air (6 in SoCal, 7 in Australia) over the last month or so, and while I basically know nothing since I was just certified in February, I'm pretty happy with the computer. The buttons are easy enough to press, and the gauge is easy to read. One issue I have is that the audible alarms that go off when you ascend too fast, or exceed a limit are pretty hard to hear in the water. When I first used it in SoCal, I was wearing a hood, so I figured that was my problem, but in Australia without a hood it was still pretty hard to hear. There's no setting for the volume of the alarm, but to compare, my dive instructur had a Uwatec that beeped loud enough for me to hear it a few feet away. Other than that, the logging mode of the Air is nice so you can review your dive profile on the watch, with depth, temp, and air (if you have the wireless transmitter) which is probably more of novelty for us recreational divers. Like someone mentioned, the bookmarking is a bit annoying when you're trying to turn on the compass, and the compass itself is a bit slow to react to new directions. Although like I mentioned, I'm a new diver, and have nothign to compare it against, just wanted to share my experiences. I would imagine for someone at my level, that even a Gecko would be sufficient, but I plan on diving more, and eventually doing Nitrox, so I wanted more feature filled computer that could grow with me.
Oh and on a side note, the strap for the Air doesn't have a wavy part to stretch when you tighten it down like some other wrist mounted ones which would be nice to keep the computer secure on your wrist. At 100 feet with my 7mm wetsuit, even as tight as I thought I should make the strap on the surface, the computer was pretty loose. Again, minor gripe, but woudl be nice for them to think about this for the future.
I'm not sure what most of you look for in a computer other than the conservativeness of the computer, but you can dial back the algorithm, but I haven't tried and I don't know how much more bottom time it gives you. Hope that helps a bit. I'm still very happy with the computer especially for the features, price, and build quality of Suunto's products.