I absolutely loved it - such a great reboot that did exceptionally well at putting a solid action-packed movie together. It was fun catching the references to S.H.I.E.L.D. and other Marvel characters. The end, in particular, was excellent. What a great way to leave your audience wanting more!
As usual, Edward Norton was top-notch. Next to John Cusack, Norton is an actor I can watch in literally anything; he is such a powerful personality. Played Bruce Banner much better than Eric Bana, who always struck me as far too strong and courageous a man than Banner was made out to be in the comics. Norton had great expressions and body language to demonstrate how Bruce felt and what he was thinking - he was natural.
Liv Tyler, while not the best actress around, certainly looked Betty Ross to me. William Hurt is a terrific actor and plays villainous quite well, but you can see there is more to General Ross than what he comes across as. As much as I enjoy Sam Elliott, he never gave me that impression in the 2003 film. And thank the Marvel gods there are no Hulk puppies in this film - it's more along the lines of Iron Man in the way it handles things.
The cameos are fun, there are some funny moments that reference the comic book persona of the Hulk (mainly the clothing), the action is a blast and the film runs at a smooth pace. Unfortunately, we have to wait a while before getting another Marvel movie relating to The Avengers. It should be well-worth the wait.