They've missed keyboard navigation completely. To be fair, there are shortcuts for many things, but it is still practically impossible to navigate the UI with the keyboard only.
For example, ⌘1 takes you to the working copy, but it only selects the "Working Copy" menu item to the left, it doesn't focus the working copy pane. The first thing I tried was to navigate the unstaged files with the arrow keys, but that just moved me back to the History view since that list was somehow focused in the background. To focus the file list, I had to press tab about 20 times to pass all the controls in the tab order on the way there.
- Ctrl-shift-+ (add file to index)
- Ctrl-shift-c (commit)
- (type the description of the commit)
- Alt-enter (validate)
- Ctrl-shift-p (push)
No mouse necessary.
The SourceTree people know how a developer works.