Sorry but concluding that the rMBP is a decent performer is plain wrong. We're developers and have been using the rMBP for a week and it's brutal. Every UI event is slow. It's choppy and unacceptable. We're running the latest DP of Mountain Lion.
Window redraws, swiping into Dashboard, bringing up the Dock, maximizing windows, etc. All slow and choppy.
This is a real issue. Buyer and Developer beware.
Concluding that every single rMBP is not a decent performer is what's plain wrong. Concluding that your rMBP is not a decent performer would be more accurate.
I'm not sure if you've even watched the few videos I've uploaded but that pretty clearly shows that 'every UI event is slow' is an inaccurate conclusion, at least in my case.