My LBS has a small fleet of Specialized test bikes available for customers to ride, including some nice 29" mountain bikes. I tried out the Camber Comp model yesterday, my first ride on a 29er. I'm not really in the market for another singletrack bike right now, but I wanted to see what the buzz was all about. The Camber is probably the closest thing to my Stumpjumper as the new Stumpy is a little more All Mountain than the Trail category of the 2008 model I have.
The difference was not "night and day", but there was a definite improvement in climbing traction and the big wheels do keep rolling along in places where 26" wheels slow down a bit. I'm not going to rush out and replace my bike, but the ride confirmed my thoughts that my next mountain bike will probably be a 29er.