I too find Git to be the kind of tool that works well through a GUI. However, I went one step further and bought Tower [1]. In addition to the many things that GitHub.app does, Tower takes things one step further. If you tried using GitHub.app, but ran up against a Git activity that isn't exposed through the app, then you should take a serious look at Tower.
One specific example is partial commits within a single file. Tower shows a diff view of edited files that breaks edits from different regions of a single file in to chunks. You can stage/un-stage these chunks right through the GUI. This is very similar to `git add -p filename.ext`, but with a very nice GUI.
1: http://www.git-tower.com
