I got my GB pro Friday, and have been playing a lot over the weekend. Overall I'm really enjoying the game. The light show and sounds are perhaps one of Sterns best. Yes, it's a little harder to keep the ball in play. I did tighten up the outlanes and that helped.
Unfortunately, I am seeing the same issues most everyone else is - balls sometime jump over the inlane guide, Slimer only registers strong direct hits, and the drop targets often don't register direct hits. I suspect Stern (or someone) will produce a fix for the inlane guides. I'm going to take apart slimer and see if the fix posted here will work (adjusting wire to the middle). And I may tighten the spring on the drops to see if that will help. Overall, I think these are pretty easy tweaks that should address the main issues.
I'm really enjoying mine, and can't wait to get home and play it some more.