Edit and Continue in Visual C# 2005!!
I really want to echo Jay's comments about the amount of herculean effort it took to get this into the product. Everyone really worked their tails off. Well done!
Why did we add Edit and Continue? Because you really, really wanted it. We're listening to you and trying to continuously build a better product. We can't add everything you want, but we'll try our hardest to make the best product for you.