There are tons of times I want to try something locally without affecting the main repository. It hurts trying to keep uncommitted experimental changes from messing up local upstream, while still switching back to the old code to fix a bug that affects everybody. With git's local branches, rebasing, and fast branch switching, it's easy to keep your local, not-yet-ready changes in a branch, and fix bugs on master, for example.

Allowing other people to pull your changes directly from your repository for testing, without committing it, is also a big plus. "Hey, I have this fix that I want to test before I commit it. Can you pull tag omg-git-is-awesome from my machine and test it to make sure I didn't mess things up?"

Overall, DVCS just fits better with the way I work. Note, pretty much any DVCS will give you similar advantages. Git's just nice because it feels fast, and I'm just comfortable with it. Plus, stuff like rebase and bisect are sweet.