About this same time last year, I bought an atomics Z2 regulator and recently, I bought the highly acclaimed T2. The T2 is the replacement for the Ti1. All of atomics regulators have the same basic design which makes them some of the best regulators available. The biggest differences between the Z2, B2, M1 and the T2 are the materials they're made from and the features each one comes with.
The top three things I like about the T2 are: 1) it is the best performing regulator available, 2) extremely light weight(I plan on going to a few distant diving destinations in the future) and 3) the swivel turret is cool.
But if your in the market for a new regulator and want something that performs as well as the T2 but don't want to pay the price for it, try the Z2.