Saw it this afternoon, and really, really liked it as well. Not sure if I'd put it quite on par with the first one, at least for me, but very close. Lots of good character stuff going on, and some great action sequences as well. I'm sure many are/will be upset with the "twist" in the movie, and I can understand that, but it seemed to work within the context of the movie. It really did have a sense of finality to me a bit as well, the ending seemed to be wrapping up the trilogy pretty well while still leaving the door open a crack as well.
As far as I have read/heard, Downey's Marvel contract was up with this movie. There has been a lot of insinuation that negotiations are in process, at least for Avengers 2, and we'll see beyond that. I know it has been said of a lot of characters, but I really have trouble seeing anyone else play Iron Man. To me, RDJ is Iron Man/Tony Stark, and I really hope he at least comes back for Avengers 2 (and 3?). If they decide to get the Iron Man franchise a rest right now, I guess I could see from the standpoint of him wanting to do something else for a bit. We will see. Sounds like this movie will be making boatloads of money, so I'm sure they'll want to make more.
As a side note, if anyone has picked up this week's Entertainment Weekly (with Tony/Pepper on the front) there is a lot of info from Kevin Feige as to the future of the Marvel Cinematic Universe. Some good info in there including Phase 2 starting with Iron Man 3, then continuing with Thor 2, Cap 2, and Guardians of the Galaxy (as well as the SHIELD TV show), and Ant Man kicking of Phase 3. There is mention of Doctor Strange possibly being a part of that next stage, and they also note that Daredevil, Punisher, Ghost Rider, and Blade have all reverted back to Marvel as well (as far as rights go).