Played a LOT of it through last night into this morning, and I'm halfway through the 3rd planet. It's SOOO worth the wait.
After that first level (same as the demo), the game is so far a pretty much unwavering 60fps. That first level in the retail has less instances of slowdown also.
Also, a full sized R&C poster just arrived today! I'm probably going to give it away since I really have no room in my house that has any space for it. I know someone out there would love to frame and hang it.

Anyone? U.S. only sorry (unless you want to chip in for shipping)
And I KNOW that some retailers have the game in stock already. They are choosing not to sell them until next week... mostly.