I've heard people say that poseidons are hard to get "right" but I have 2 cyklons that areover 5 years old and they have never free flowed, froze, or caused me to breathe hard. I will admit the cyklons are stiff untill you get below about 30 feet but at that depth I'm either coming up on a deco rig or dropping down quickly past it on my way to the bottom. they wear like steel, are easy to adjust the cracking pressure, are impossible to over breathe and are very compact in the first stage. And since they don't have an up-down or left-right they work just as well if you have to turn it upside down to share with another diver... try that with your apeks and you'll get a mouthfull of water with each breath. Oh, and I can configure my regs so one comes over each shoulder. That way I never have to think which reg goes with which first stage if anything ever happened. I'll never get rid of my cyklons.
For deco I just got an OMS O2 reg. For an unbalanced piston it's a remarkably good breathing regulator. I'm not sure who is making the regs for OMS but for $140 from LP it can't be beat for an O2 ready, color coded reg straight out of the box.
Was using an oceanic alpha for deco but cracked the second stage when someone (thanks lou) dropped a tank on it on the boat. To get a new body and overhaul both the first and second was $110. Brandy spankin new deco reg was $140... no too tough a choice.