> Have you noticed any speed decrement in your learning curves (learning new languages or frameworks)?

Hard to tell, but a speedup if anything. Once you know 5 or 6 languages, another one is pretty easy to pick up by looking at it.

I've posted elsewhere: Most recent endeavor is RoR, and that was fast. It's hard for me to differentiate whether that's because I'm Mr Smart&Experienced or because Michael Hartl rocks. I suspect the latter.