So RocketNinja is a git shop thanks to me. We climbed from being a perforce shop when I took over server developement here. We use github, mostly just for the safety of having a remote managed repostitory rather than any of their add on features.
Github: Git on the web. There’s a built in tree and source viewer and editor, an inline code comment features hooked to email. The pull request feature is amazing. Branching and merging across many repositories can be a challenge to an organization. Trying to perform code reviews on changes eminating from GMT+2 in GMT-8 is a pain. Pull requests fix that, completely.
Gitorious: github as open source. Almost as good, and deployable by you and me on our own servers.
Tower: Easy. Efficent. Powerful. Boloney! Awfull visual design, poor task flow and ugly as sin. It’s so busy that even the easy tasks are hard. Thanks guys.
SourceTree: hey, it’s got mercurial support too! Other than that it’s a big WTF.
Gitbox: What’s cool here is nothing. The nice empty space, the minimal controls and focused design. Gitbox does the 90% subset of what you need from version control and leave the rest off. Two lists, a list of changes and a list of content of those changes (or, at the top of the timeline a list of pending changes). Create, switch, pull or push from your branches and remotes. Commit as well. The winner by far.
GitX: The standard when it comes to viewing history, not fancy or complicated. It does one thing and it does it … well ok. Oh and it’s open source, so if you feel the need you can make it even better.