I have an atomic regulator from GLA as well and I've got to say its one of my favorite regulators that I've purchased from them. It's very well-built and the needle valve allows for super-fine adjustment. They also look really cool!
Regarding bubble counters, the in-line type work just fine. You can hide it in your stand or attach it to the side of the aquarium. It really isn't too big of a deal IMO.
You can use these regulators with a reactor, but to be honest the atomic diffusers that they sell are going to be much, much more efficient than MOST reactors. I had a reactor on my 90G and I recently switched to a 45mm GLA atomic diffuser. I'm using about 1/3 the CO2 (BPS) with the diffuser compared o with the reactor, and i'm getting the same concentration level in my aquarium.
FYI, unless you were using the same working pressure with your reactor as you're using with the Atomic diffuser and you've not had to increase your working pressure substantially to accomodate the diffuser, then you're not using less CO2. The bubbles may be the same size but increasing the working pressure from 15 psi to 35 psi means you have a larger amount of CO2 occupying the same volume. It was discussed ad nauseum on the forum when the diffusers first came out.