Linus Torvalds recently (2007-05-05) gave a presentation about GIT at Google. The video of the presentation is available on youtube.
In this particular presentation, I found Linus to be opinionated and rather unconvincing. He is extremely critical of CVS and Subversion. While GIT may be well-adapted to Linux's development model, I believe Subversion get the job done in other environments.
Martin Tomes, in his comments about GIT, nails the point. GIT and Subversion aim at different development models. While not perfect, the classical (centralized) model works well in both large and small projects, open-source or not.
The GIT project publishes a detailed albeit biased comparison between GIT and Subversion. The comparison makes a convincing case on why GIT offers better support for merges. The same page also mentions that the user interface for Subversion is better.