My company is using it for all our projects now and we are absolutely loving it. We are also using GitHub for remote storage of the git repos, you should look into it. It has a nice interface and personally I like having an RSS feed that shows me all the recent commits.
If you have questions about Rails and git you can come hang out in #github on freenode. There's usually some Rails core members or Rails plugin authors there that are experienced git users.
Moved over from SVN to Git for all of our Rails projects. Plugins? Doesn't matter if they're SVN/Mecurial/CVS/Git whatever. Once you './script/plugin install' the plugin is in your vendor/plugins dir. Git plays well with SVN. Give it a whirl.