I have encountered a bunch of bugs with Mono but only on my Win 8 machine. My Win 7 machine runs it with no problems. Copy and paste gets screwed up and it pastes gibberish and not what is on the clipboard - I tested this by pasting it into a note pad document and it pasted what it was supposed to do. Sometimes I need to manually refresh in Unity to register recent changes made in Mono. Occasionally, it just refuses to open at all when I attempt to edit a script. I know I’ve encountered other minor nuisances but those are the ones that reoccur fairly regularly.
Delete sln and csproj files, change that config option from ‘Custom’ to ‘Mono’ or ‘Microsoft Visual Studio’; then sync monoDevelop project in Unity.
Will be easier to work with MonoDevelop that way. But the bad performance that some users have I don’t have, so can’t help with that…