Well I agree with sjt19 in some aspects but not others. I have had a few Angel A.I.R.s and I have found them to be 100% reliable and never had a problem with them. I've never had leaks at all.
I have had the occasional leaks from Geddon's and Max Flo's but as with most air systems once you understand each systems characteristics they are often simple to trouble shoot and then keep working hassle free.
However, to agree with sjt19 I think they are very heavy. I also hate that you have to turn them on and off with an allen key every time. I switched to the Mac Dev 03 Conquest system from an A.I.R. for the following reasons...
1. A MacDev Conquest 03 reg is about half the weight of the A.I.R. reg.
2. Conquest03 has a built in on/off
3. Conquest03 has a built in air vent so that when you turn off the air system you don't have to dry fire excess air from your marker
4. Conquest03 has tourney locks for output pressure. Once it's set to your liking you lock it in place and never need adjust your output pressure again - EVER!
5. Conquest03 doesn't have any batteries that can run out.
6. Conquest03 has gauges that whilst uglier than the A.I.R. means I can always take a quick look at my pressures mid game to see how much air I have left
7. Conquest03 is a smaller profile
8. Conquest03 can have the gauges mounted either side of the reg meaning it's just as convenient for left and right handed folk
9. Conquest03 comes with it's own dovetail mounting system again creating a tighter set up (a more personal thing that though)
10. When initially setting up output pressure it doesn't require the use of an allen key
That is not to say anything beats the AIR performance wise as I think it is equal to almost every air system out there but they were my personal preferences as to why I switched away from it. Hope that helps.