Sorry for the delayed response. Yes, there are a few reasons we haven't upgraded. DF 2010 requires .Net 4, which requires purchase of VS2010 for all of my devs, plus a new set of licenses for our source control (which doesn't work with VS2010), plus new expression blend (we are using WPF) plus the T4 generator changed the naming for all of our navigation "ID" properties from "something_FK_something_ID" to just "somethingID" which would require overhauling a TON of XAML (we have 400+ entities and scores of screens).
Maybe I am mistaken in the requirements above? We DO eventually plan on upgrading but we are already late on a project and fear this would cause even more havoc/delays..