For reasons best not examined too closely I switch between between Mac and PC which, since I earn my crust largely with .Net development, means switching between Visual Studio and MS.Net and MonoDevelop with Mono.
Mono is very impressive, it is not at all a half hearted effort, and it does some stuff that MS haven't done. But when switching environments, there's always the occasional gotcha. Here are some that have got me, and some solutions.
Gotcha: Linq Expressions don't work on Mono
Solution: Add a reference to System.Core to your project.
Question: What version of NUnit is built in to mono?
As of Feb 2011, it's nunit 2.4.8.