Having seen Harry Potter & Chamber of Secrets... yeah, well. They left a bunch of stuff out for no particularly good reason. I mean, seriously left out in ways that made things seem choppy and confused, and destroyed the foreshadowing... and then the curtain call at the end was so treacly-sweet and overdone that I nearly lost it. It's like the whole point of the 'Gilderoy Lockhart' thing was just utterly missed by the producer, that shallow flashiness doesn't measure up. Pfui.
Definitely worth staying through the credits. If you didn't, shame on you, you should go back and see them.