Yeah, buying a revision 1 apple product has been a bit risky in the past, and if I buy now, I'm getting a known quality. Still with the possible 15 - 25% performance increase some have estimated, it might be a wise move for me to hold off. The addition of USB 3 is icing on the cake.
As for the case redesign, apple has shown an unwillingness to make a change until it absolutely has too. Just take a look at how long the pre-unibody MacBook Pros had that design, it was from the G4 powerbook days. The Mac Pro's design itself is also from the G5 era as well.
I have a core i7 desktop that I upgraded to Lion recently and I'll use that as my main machine until Ivy Bridge comes. If my 2010 MBP was the only machine I had, then I'd be more inclined to get one now.
Personally, I would just like to see Apple couple Ivy Bridge again with a lower power but still good enough (and faster) GPU, much like the base 15" that I have now. And expand the battery while decimating the OD. That should make battery life better by another 2-3 hours.
The performance gain doesn't look to be more than 10% to me. The limiting factor has always been heat and cooling efficiency. Turbo rarely kicks in even though I rarely hear the fan go. An even hotter system would go into Turbo even less.