I'm running it under 7.2.2. I am not seeing any problems with slowdown though I think the resolution is small and the game crashes when you try to change resolution (I might try that again with different settings). It also crashes for me when I try to reassign keys to non-modifying keys (this is a general workaround for problems with Pro Pinball, not just on Crossover).
But the big news is that I think there's a workaround for sticky flippers! I noticed that the keys only seemed to stick when it really mattered -- and did some experimenting, and noticed that it wasn't generally sticking, it was just that you couldn't operate one flipper while holding the other. Which would, indeed, make it unplayable. But if I operate the right flipper with the shift key, and the left with CTRL, then all is well. Does this work for you?
Now my only remaining problem is that the game is beastly hard and it keeps stomping me.
I am running it on a shiny shiny new 2.8Ghz MacBook Pro.