IntelliJ is better on Unix than Monodevelop - there is still no end to end story for *nix developers backed by MS (compared to something modern like Dartlang)
Monodevelop/Xamarin Studio does indeed have a long way to go. Do you know about the open source project OmniSharp? http://www.omnisharp.net/ which provides xplat development toolchain. .NET in Sublime Text/Emacs/VIM yep. It was created and maintained by both employees of MSFT and the OSS community.