I just discovered Sublime Merge today, from a note in the ST changelog (3200), and so far it's comparing very well to SourceTree, which I've used for years. I'm really liking the diffs, in particular. And I'm excited about the built-in merge functionality (can't wait to run into some hairy conflicts! lol)
One thing that I've noticed, however, is that I find I keep making the window reeeeeeeally wide when browsing through commits. I like the 2 column diff option, but that means the window has to be wide enough for long commit messages as well as 2 columns of source code...and then there's the Location sidebar, if there's any room left over
From what I've seen here in the forum, there are several undocumented prefs that can be set in the JSON file, so I don't know whether there is currently an option to adjust the layout so the tree view is stacked on top of the commit view (similar to SourceTree), but if there isn't, please consider this a feature request.