Ok, now that I have given it some time to settle in my system I think i can give an accurate review of my Iron Man experience. First things first, I thought it was great. It was a terrific movie going experience for me. Because I am not an overly avid reader of the Iron Man comics I can't say whether or not Robert Downey Jr. gave an accurate portrayal of Tony Stark/Ironman, but I can say it was a performance well to my liking. He knew when to be serious and he knew when to witty and funny. I would almost equate his performance to the Toby Maguire's in the Spiderman franchise in the sense that both performances create a nice balance of both serious and funny characteristics. This can also be said for the tone of both films. I have read complaints about the movie not having enough action. I found there to be the perfect amount of action. The way the action sequences were dispersed throughout the movie created good pacing.
I was expecting Tony Stark to be a little more of a struggling alcoholic, but after viewing the movie I think it would have been hard to portray him as a likable hero with an alcohol problem. There are just some things that work better on paper than they would on the screen.
The amount of Favreau in the movie was tasteful. Gwyneth Paltrow provided depth. Leslie Bibb was hateable, which was nice because i'd had enough of her on LOST. Terrence Howard had a great performance playing the "buddy" role, and will be great "next time" around as War Machine. Jeff Bridges didn't surpass his role in The Big Lebowski, but still proved to be a great addition to the Iron Man franchise.
I was surprised that they would adopt some of the lore of Iron Man from the Civil War comics. I guess I can't say that it is a direct reference, but Tony Stark revealing himself as Iron Man read a little Civil Warish to me. I found it to be a huge shock. I'm not dissapointed with the decision, I think it will make things interesting for the next movie.
Now, on to the clip after the credits. I don't think I have been that excited since the first time I saw X-Men in the theater. To know that there will be an Avengers movie that pulls together some of the most iconic characters in comic book history is just tremendous for me! Rock on Samuel L. Jackson!
Also, how did I not catch that Strategic Homeland Intervention, Enforcement and Logistics Division stood for S.H.I.E.L.D. ??? I mean I know it was the first time they had the acronym stand for that, but still, I should have caught on. Boy do I feel sheepish.

[EDIT]
SX0T here, I'd have to say that I agree with most of the above comments. I think that this is the best superhero movie we've gotten so far and that is a tough decision considering X-Men II and Spiderman II. I also find it a bit strange that the best we have gotten so far comes from a lesser known Marvel character when compared to the X-Men or Spiderman. RDJ knocks it out of the park as Tony Stark, no question. I think Favreau was a bit unnecessary, but it's his film and I would have done the same. Terrence Howard was pretty awesome and will be even better "next time around". I still have a little trouble seeing Jeff Bridges as anyone but "The Dude" but he still did a great job. As Derek said however, the great part was Sam Jackson informing us that Avengers is on it's way.