I have mspec running with R#, but my client doesn't have R# and doesn't plan on getting it. :( I want my test suite (written completely with mspec) to be valuable to my client, so it would be HUGE if the VS2010 test runner ran specifications written with mspec. Is it possible?
Running MSpec in the VS runner is not possible. You can set up MSpec as an external tool that runs the current assembly in a separate console window (free), have your client purchase TestDriven.Net or convince him to invest in ReSharper (I'm sure we both agree the tool is worth its price :).