Only 70 votes so far for covariant return types in C# (and all .Net languages)!! :-(
I thought that there was a lot more interest than that.
Here's a chance for you to really show what you're interested in seeing. If you haven't voted yet, and you do care about this, do it asap:
If you go to this page you can submit your vote: http://lab.msdn.microsoft.com/ProductFeedback/ViewFeedback.aspx?FeedbackID=FDBK16960