I have one customer using thin clients to connect to Remote Desktop. The biggest issue is with multiple screens: RD sees two screens as a single, really wide screen. I seem to recall that maximizing works OK, but when there is a dialog box, it pops up in the center, right where the two screens are separated. That is a pain, and they don't like that.
I have a couple of other customers running MAS90 as a RemoteApp on Server 2008, and they like the speed of RemoteApp vs running it as a local application. Hope that helps.