Another item to consider is looking into GitFlow. It is not a part of git itself and is just a way to work which survives in complex dev environments. See: http://nvie.com/posts/a-successful-git-branching-model/ for more information. It is pretty similar to how we ended up doing things on some insane large projects I've worked on but with the addition of some scripts: https://github.com/nvie/gitflow#readme, it makes things fairly easy compared to our adhock methods in Perforce. An added benefit, if you happen to use Os X, SourceTree (my favorite git front end for OsX) integrates the scripts directly. Point and click git flow is really sweet.
Wow, GitFlow makes working with development branches really nice. I've been using GitExtensions because it provides an easy interface for git and I like how it presents the repository graph. I noticed that there's a request to integrate GitFlow into GitExtensions, but it doesn't seem like anyone is trying to implement it. While GitFlow would be really nice to use, I'd rather stick to GitExtensions for now than go back to using the command line for Git. So far I'm really the only one working on this project, so I'm the only one modifying my repo. I will of course adopt the same branching model into my project though. Also I'm certainly open to recommendations for other Git GUI extensions, especially if they have has successfully integrated GitFlow.
It seems like SourceTree (http://sourcetreeapp.com/) has already integrated GitFlow into it's Mac version, and are working to get their Windows (beta) version up to speed. They're not quite there though, so I guess I'll just stick with GitExtensions for now. I also came across an article by Scott Chacon, where he talks about an alternative version control scheme to GitFlow. His team uses it at GitHub. Here's the link for anyone interested: http://scottchacon.com/2011/08/31/github-flow.html. I *think* the GitFlow model still seems more fitting for my project though...
Also although I'm writing an editor, I'm also building engine code in the same solution. I ended up having separate local repos for each project in the solution. Is it recommended to have one unifying repo instead? It would definitely make keeping track of changes much easier (since there would only be one repo to commit to), but I don't know if there's a big negative that I haven't thought of.