I've been processing with nitrogen now for about 6 months in a 3.5 gallon tank and have had great results. There are some tweaks necessary - for one, I use a roll film rack that will hold 30 rolls, but the bottom course of film won't develop well, so I insert a course of 120 reels in the bottom to take up some space and that took care of everything.
My Gralab is the timer which provides power to a Ted Pella gas burst interval timer. It is nice to set the total time, switch out the lights and then submerge my film (sheet or rolls) and start the timer. I just sit there in the dark and listen to the gas turn on and off.
I process in HC-110 dil B at 75 degrees - I use a refurbished Calumet temperature regulator/recirculation unit to keep the chems spot on. I have noticed that the gas-burst makes the HC-110 foam up (like a beer), it doesn't seem to have a negative effect on the film, just something I noticed.
My burst/interval timer has two sides, so you can switch from nitrogen to oxygen - which is useful if you want to use oxygen burst to agitate the fixer (fixer does not oxidize like developer).
Read the Kodak pamphlet very carefully and obey all their recommendations. They specify that the gas plenum holes must point downward and that it must be ½ inch up from the bottom. When I got my Arkay tank/plenum in the mail - the plenum was installed wrong. Also, the interval they recommend is 1 second of burst every 10 seconds. I started out doing 2 seconds every 10 which used up my nitro twice as fast.
Michael Kadillak helped me A LOT in setting set up and was very cool about answering all my questions. He hangs out around here so he should be pretty easy to find.