I recently got to test drive both cars side by side. I drove the standard first and was totally blown away by the power. No more driving I'll be flying! When we got back I nagged the sales guy to let me try the performance right after. I got a smaller test drive in the performance but it was enough to see the difference. It was a little nicer off the line and I definitely felt the acceleration a little bit more. The question is, was it worth the extra 10k. Honestly I don't know if it was but frankly I don't care, I'm buying a performance. Also a standard fully loaded with 21" rims is already in the 90k mark and if you have that kind of money why not spend a extra 10k. Bottom line I felt enough of a difference to justify the cost, plus I think I want those carbon grey rims with my black model s.
Down side is I have to wait a year