I'm a happy SourceTree user as well. I know how to use Git in the terminal but I find SourceTree quicker to use as it lets me quickly visualise what I need to see.
- new branches (I find the syntax tedious for some reason, and I like to see where I am in the tree, so I'm already looking at SourceTree's interface when I'm branching) - deleting remote branches (see above about syntax) - awesome diff visualization for past commits and current work
Everything else I do on the command line, because SourceTree requires just a few too many clicks for my liking. It's a shame the terminal can't have a nice diff interface like SourceTree's, otherwise I'd probably be full terminal.