Using Git on the mac feels like a huge pain, and the Git documentation is just huuuuuuuuge. Maybe someone has a top secret blog article or even screencast to share, that explains the basics fairly simple and quickly?
Creating a repository. Big pain.
Opening that repository with GitX: Pain.
Working in Xcode and then committing changes: No idea, probably big pain too.
Cloning the repository to a few other developers with their own macs so they can start collaborate on the project: Oh man, my head explodes... need a doctor!
Merging those cloned repositories back somehow, so everyone gets an updated repository with the changes of anyone else: Red alert!
Right now I feel I'll need a month to grok it. Would be SO glad if someone can point out really helpful resources that don't force me to read for some days... or is there a great and thin book that explains this madness?
Git is absolutely enormous, and you could certainly spend that month learning its processes, but you can stick to some basic concepts and end up with a really great workflow. I use the command line, as it allows you stick to these basics, and expand out if you need to. These basic commands are "pull", "push", "init", "commit -am "message"". Later, you can read about branches and rebasing at gitref.org.
As a mac Xcode + git user; I definitely recommend DTerm to make life easy. One key command brings up a floating terminal window, CDed to the directory of the file that's currently active. In XCode, this means that you'll be in a git-controlled directory immediately.
So, my workflow --
I find that the command line allows a much easier working relationship with git than GitX, especially if you're using something like DTerm.
For a great reference, check out gitref.org. Good luck!