Just a small suggestion I've been thinking about.. I think having non-regenerating health/armor percent meters along with health/armor pick ups simply makes a game more fun. The way Rage is, you are forced to hide around a corner and wait until you are normal again after just being shot a few times. I find myself doing that a lot. Or like most of the way through Rage, you only get hit like every now and then, which is no big deal because you know you will just heal right up.
Health/armor meters makes it so every hit you take from enemies means something to you. A lot of times in Rage it doesn't bother me that I get hit a lot, because I know it will just heal up quick. If you want the game to feel more realistic and rewarding, then bring back the health/armor percent meters, along with health/armor pick-ups! Having non-regenerating health/armor meters also makes a game overall more challenging and exciting.