I've already explained my qualms with CG, so I won't get into that here. I will say, though, that The Avengers has easily some of the best CGI I've ever seen. It's definitely not perfect, especially when Jeremy Renner and Scarlett Johansson were onscreen, but it's pretty damn amazing. Mark Ruffalo's Hulk was especially good, and now I know why. The team used a combination of ridiculous outfits, some kind of Ruffalo-based performance capture, and really intensive animation to make something really awesome.
The video above shows some of the work that went into it, and it's really cool to watch. I especially liked watching the guy in the Hulk suit doing his thing.