I have an Atom 3.0 (actually, I got two, one for my son as well). Although I don't have a great amount of experience, I generally like the Atom pretty much.
I had been concerned about seeing the display (55 year old eyes, nearsighted, but with contacts..) but it hasn't been a problem in practice. It seems to support everything I would need in the near future, up to three tanks (The 3.0 has a "buddy air" feature so I can check my son's air. Patent conflict caused that to be removed for the 3.1, alas.) It has a plethera of alarms (max depth, max time, min air remaining, and more. It's a bit harder to hear the alarm than I had expected, so I don't know that it would get my attention on its own, but periodically checking it reveals when it's getting upset. With three lines of display, it takes a little getting used to it to know what it is telling you in what situation and how to move through the different screens..
We also have BUDs as backup computers, which has a similar display scheme and the same algorithm as the Atom.
We have never had anything more than a momentary drop-out from the transmitter. The computer is programmed with the transmitter's ID code, so there is no dynamic pairing that can screw up and pair with the wrong transmitter. I do, however, wish that there was a button on the transmitter to manually turn it on. It's activated by air pressure, but I don't have a tank at home and it would be convenient to have some way to test the battery level before a trip. The battery in the transmitter and that computer are easily replaceable, so I carry spares, but have never had any problems with batteries.
I download data with subsurface, which has been working well for me.
Overall, I'm quite happy with them and would definitely consider it a strong contender if I was looking to buy it again.