Great reg, no question, have serviced hundreds of this model.
1st Stage.
HP seat is one of the best in the industy in the hands of an abusive divemaster can last over 1000 dives and not fail.
Itermediate pressure will not creep.
Chrome is some of the best on the market today.
The enviro seal will start to bulge after a while, this is normal and is replaced at service (caused by ware of the primary diaphragm).
2nd Stage.
Phnematicaly ballanced venturi assisted, performance is equal to any other 2nd stage on the market, adjustments are easier to use then most.
Works great in cold due to heat sinks on both sides (adjustment knob is metal for a reason!).
LP seats used by Apeks are kind of crappy and has no seat saving device built in like Atomic and Scubapro. Make sure you store it with the adjustment all the way out!
The venturi system on these are prone to getting sand in the workings (your fault not the regs!) Adjustment will feel gritty and can cause wet breating, keep it out of the sand!
Early ATX's used a rubber (ish) inhalation diaphragm (junk) make sure you have upgraded to the new Aqualung made silicone diaphragm (came out just over 1 year ago), not a warranty part so dont expect old ones to be replaced for free.
Exhaust valve is made from rubber (ish) and is not part of the annual service kit it will go bad after about 2 years, expect to see Aqualung replace this for there silicone LX/Legend Valve soon.
This is one of the best regs on the market today, Reliability, Performance and Cost have made this one of the fastest selling regs world wide. Since its introduction in the Aqualung line up the Apeks brand has become a real Scubapro killer. We are now servicing more Apeks brand regs then Scubapro's!
Enjoy!