Since last year I'm using MonoDevelop for a few projects and it is the best IDE I could never use because it's very simple and useful at a time. It has the few things I need for manage application development and its editor is very nice with a few helpers like code completion and auto-indenting features. Since 0.9 release it has easy support of plugins that makes it very extensible... ready to grow.
Today I've got a problem after my daily upgrade of Ubuntu Dapper, when I go to edit references of a project it crashes. Looking in the stack trace it seems to be some rendering of an icon, it is very strange and I think that there were no upgrade of MonoDevelop dependencies (only X packages). I recommend MonoDevelop and Dapper users don't upgrade and if they upgrade, take care of what breaks MonoDevelop and rever to the older package of it.