I've used GitX on and off, but I have yet to find a feature compelling enough to use the graphical interface over the command line.
The search feature is probably the most useful, but there's not much there that can't be hacked together in a five-line script.
Now, don't get me wrong. The work that has been put into this application is great, and has come a long way since I started using it (around the 0.6 release, I believe). For people who prefer a GUI interface, I don't think you can do much better on OSX. However, you haven't done anything to sell command-line users on it. If that's not your goal, then there's no problem. If it is, well, I haven't been convinced yet ;-).