An ASP.NET web developer, now working in ASP.NET MVC.
For over a year, my .NET skills were blunted by the necessity of working almost exclusively in ColdFusion. Still, it gave me chance to get to know MVC a lot more through that sites use of it. When ASP.NET MVC came out, I felt I had a good advantage, and had a stronger knowledge than if I had continued using webforms. I believe that now though, my strengths lie more in the architectural pattern rather than C# itself.
I've answered more questions in the last couple of months on StackOverflow, than I did in five years on the Experts Exchange.