I've now managed to build MonoDevelop without the dependency on X11, and it looks so much prettier!
I followed the steps on NaizNoiz again, although I actually used the pre-packaged Mono installer as suggested in this comment rather than installing this with MacPorts.
I have noticed that the font used for the code has some slight alignment issues, it can be seen on the lines that read:
var eyes = Enumerable.Range()
.Select(i => i + i);
So I might try to find a fix for this at some stage. Although I think my priorities should be trying to get familiar with using MonoDevelop and it's underlying architecture. So to that end I've decided to take on a little project to produce a simple app. I'm going to try to make it run on both Windows and Mac, as I think that'll be an interesting and educational exercise. The backend will be SQLite probably with NHibernate, although I might try out SubSonic if that looks easier to get started with. For the frontend I'm not sure whether to use ASP.NET MVC or just do a desktop app.
I'll let you know how I get on...