First impressions:

I open the new file dialog. Type in a name, try to copy the name... and it closes the new file dialog! Apparently Cmd-C is bound to cancel. Okay, so it's a little quirky. Let's try again.

I create a new file. Type some text. Select Edit->Copy this time and... it's crashed.

Maybe I'm unlucky.

I install MonoMac, restart, create a project, write some code to display an NSAlert, press build and

    Build failed. ~/.config/MonoDevelop/addins/MonoDevelop.MonoMac.2.4.0.5/mono-version-check does not exist.

Jesus

EDIT: As a bonus, a process called mono has been running at 100% CPU for the last half an hour.

EDIT 2: After using it for a bit longer, the editor itself is actually not bad. It has all the features you'd expect and autocomplete seems well implemented. But this software is just far too buggy for any kind of serious day-to-day use.