Edit and Continue, conspicuously absent from Visual Studio .NET 2002 and 2003, is finally here in Visual Studio 2005. A few minutes ago was the first time that I have used it a .NET application, and it sent shivers of joy through my body. Edit and Continue is a fantastic feature that lets you change code as it is running. Forgot to check if something is null? Just slip the check in and hit F5 again. You can make almost any change you want, and don't have to recompile, restart, or any of that. It makes debugging so much more productive.
I can't wait until I can port IvoryTower over to .NET 2.0. There is simply too much programming goodness in Visual Studio 2005.