I'm not sure how far back this feature goes but I just discovered it yesterday, thanks to Michal Talaga.

When you follow the practice of defining your test before you write your method, you lose out on the beauty and addicting convenience of intellisense.  Since Visual Studio.Net v1.0, I have become dependent on intellisense to keep me productive and assist me in typing out long method names.  Having to type them once, and then again, sucks...

WOW, check out what is available when you write a method that doesn't exist!

Now I seem to recall running across this before but I was not yet privy to TDD.  As it turns out, this is even faster then waht intellisense gives you because the method signature is shaped according to the variables you pass in. 

Try it out and see if you don't also feel it was the missing piece of your TDD puzzle.