Awesome, with a few flaws
I remember playing Rage 1 and thinking it was an awesome game. Rage 2 is awesome too, but... it's essentially the same game as the first.
The melee weapons don't seem to have any combo effects, and, for the number of guns you have, they all seem to do the same thing, with relatively simple animations. I was kinda hoping for some true laser beams and BFG effects, but, I realize that's just my personal preference.
I have a little bit of commentary on the "rage" bar as well. It's been a while since I played Rage 1, but, as I remember it, it was a lot easier to get the bar going up - either the increase rate was a lot faster, or the decrease rate was a lot slower. In any case, in Rage 2, the special attacks became a very rare occurence, because I could never seem to keep the bar high enough to use them. Don't know if that's what you intended, but I found it a little disappointing.
The biggest problem with the game is the rendering. I'm running a 3 gHz processor with a Radeon X800 and a gig of RAM. There's no reason a flash game should be slowing down on me, especially not to the 1/3 speed gameplay I was getting. Now, I don't know much about flash, but, in general programming terms, this probably means that your code is a bit chunky - excessive memory use. The objects you have Flash rendering are probably taking up more memory than they need to be. I'd love to tell you how to fix it, but, as I said above, I'm not familiar with Flash's programming.
Besides that, great game. Keep up the good work.