This happened a lot to me while I was working at my previous gig.  Someone would explain that they had a really cool method of working with something inside the .net framework then someone would use the line "but reflection is slow, so we can't do that in our app" or something similar.  And I have run this test multiple times and built several test cases to prove it.  But it all boils down to this, if reflection was slow, the .net framework would be slow.