I started to use git a few days ago. I’m still a fan of Mercurial, but git turned out to be “a must” due to the number of “Battle of Wesnoth” developers switching to it, and thanks to rather seamless integration with Subversion.
The other reason is that I’ve been looking for a DVCS tool to use as a front-end to an SVN repository I use at work, with a possibility of converting at least one other open-minded guy to that paradigm. Of course, in this case solid integration with the existing (and mandatory…) tool is a must, so git scored an another point.
So far, it seems to work, and reasonably fast at that. Getting it to run on Cygwin was a pain in the neck, though, because for some reason git opens its internal files in text-mode (ugh), which leads to problems with index getting corrupted (CRLF/LF) if Cygwin file systems are not mounted in binmode. Careful there.
I’ve also hit a problem with Subversion import, most likely caused by some branching mess in our development history (empty directories being created in branches/ with no data, then being deleted, then being recreated as proper branches). Don’t ask why it’s like that. I probably have a bug to report, once I have it tested on a simple test case. As it is, inspection of the branching history shows branches where nothing has been branched, and merges when a branch was created. Ouch.