I converted my main .NET solution I'm working on from Visual Studio 2005 to Visual Studio Orcas without any problems.  I did the conversion so that I could play around with LINQ, and more specifically the LINQ to NHibernate adapter, and as such I chose to run everything under .NET 3.5.

I thought for sure I would get at least one conversion error or compiler error, but no.  My solution even included NHibernate and Iesi.Collections.  Better yet and possibly even more suprising is that I can still run and debug the web project which is using MonoRail RC2.