I consistently hear good reports about Atomic regulators but have never used one. I haven't particularly heard reports about any Zeagle regs, and I've never used or even seen one.
What I look for in a regulator is first and foremost ease of breathing, secondly consistency in breathing, (3) quality and robustness, (4) consistent performance throughout and well beyond the normal service interval, (5) compactness and lightness, (6) price.
Particular regs I have liked very much have been Poseidon Jetstream (my overall favourite, though not what I tend to use most) and Aqualung Titan (the cheapest model, the basic "Titan"). Although I like the idea of Apex regs I have never particularly liked any that I have actually used. I used to sell Scubapro and used many Mk25/S600's, but I have to say I don't like them and never use them out of choice. I still own a Mares MR22 and like it very much, but it feels fragile (all too easy to damage the HP seat) and is very heavy.
The Titan I'm using at present is quite remarkable. It delivers air at a very reassuring pressure regardless of depth - I've had them below 400ft with no problems - and is incredibly tolerant of lack of servicing. The one I currently use for warm water recreational diving has not been serviced for over 3 years (well over 1000 dives) yet performs as new. But for cold water diving I reach for my Poseidons.