After the last couple posts on O2 and OSX I decided to have a quick go at running the main O2 C# REPL on my Mac and was very pleasantly surprised when it worked!!!
Here is a screenshot of the PoC - Roslyn C# ScriptEngine Execute v1.0.exe (which you can download from here) :
Note how you get the AST errors:
Which means that the Roslyn dlls are working ok (since this REPL uses Roslyn to find out what where the AST errors with the script to compile)
This also means that the SharpDevelop Editor now runs on OSX (which before it didn't).
I'm not 100% sure if it works now because of some updates on the latest version of Mono, or if it was the XQuartz installation that did it (see Problem running O2's Exe on OSX 10.8 , fixed using XQuartz ).
There are still a couple things not working (like the code complete window doesn't show up), but it is defenitely a massive step forward