The characters of Giant Man, The Wasp, Nick Fury, Captain America, and the Hulk were fleshed out and realistic, but a lot of the bits with Hawkeye, Black Widow, Iron Man, and Thor skirted the edges of self parody.The dialogue was often too hip for its own good, but had its moments. Millar's very good at handling action packed events, and this was no exception, with the plot moving along at a brisk clip. It was refreshing, after reading a lot of talky DC comics events, where the fights scenes and action sequences weren't as emphasized as the plot exposition, to read the well written battles that fill this book. Bryan Hitch's art for this series reminded me vaguely of J.G. Jones, which is a good thing, and carried the weaker sections of the book.
Overall, I thought it was great fun, and a good jumping on point for the Avengers mythos in general, and if you liked the Avengers movie, chances are you'll like The Ultimates.