NUnit vs MbUnit, lets not.
There is a wiki thread discussing MbUnit vs NUnit. I tend to avoid comparing both frameworks when our aims are to achieve the same thing, test software. Long term we do aim to to use the expansion hooks in NUnit so you can hook in MbUnit to NUunit (in much the same way Charlie explains CUnit and VSTS). MbUnit is now a open source project and under a similar license to NUnit, the details of that license will be added to the wiki and CVS ASAP. I welcome Charlie and the NUnit folks to share, contribute and discuss.