I have an Atom 2.0 that was my first computer and I found it to be a great vacation watch (so I didn't have to worry about losing my expensive watch on a trip). The atom 2, although a great computer in such a small package, is really confusing to use, is a pain in the ass to take off when also taking off a wetsuit, and a bit on the small side for my aging eyes. And, did I mention it is confusing to use?. So I recently picked up a used VT4.0 and now I just tie my atom to my BCD as a back up while diving. I did have an incident a couple years back where my atom died on me in the middle of a night dive, so a 2nd computer was on my list. I also have a small SPG as well in case my transmitter goes.