The primary goal of the Pathfinder RPG isn't to 100% reinvent the game. The rules in the Beta were (as they should be in a Beta) experiments. We've seen that some of those experiments work out, but others don't and we're reverting back to the 3.5 rules in some cases. In the end, the game is hopefully going to be very compatible with 3.5. As a result the Pathfinder RPG is probably not the game folks who are totally fed up with 3.5 and hate the 3.5 rules are going to want.
As for how much time a GM needs to prepare monsters and build adventures... there are some adjustments here and there, yes. We're deep in the process right now of creating the monster stat blocks for the Pathfinder Bestiary, in fact, and after having statted up 60 monsters... yes, building stat blocks is faster and simpler. It's not fast and simple, though... and honestly, I don't think it should be fast and simple to stat up an entirely new monster. I don't see a moderate level of complexity with RPG rules as a problem but as an attraction, and I'm pretty sure I'm not alone in that camp. There's a happy balance somewhere between complex and simple, and that's what we're aiming for. The 3.5 rules as they currently stand are too much on the complex side, but I don't want to overcorrect into the simplicity.