Well, power of computers doubles about every 18 months, they say. But developers don't get faster at the same rate. So, I see creation of frameworks that increase effectiveness of developers as a good thing (even if these frameworks add some overhead to programs). You are probably aware that similar things had been said about C++ by C programmers. Why make religion out of programming? I think the most important criterion in most cases should be whether it's good for business.

As far as performance is concerned (at least, that of C#), take a look at Does C# Measure Up? (why isn't this link rendered as one?... suka)