Don't have a 29er full suss, but do have 2 29ers. They're great bikes and climb almost as well as a 26er. The extra weight at the front IS noticable (even with light wheels) and makes it *slightly* harder to trackstand, hop about and flick the wheel quickly.
Truths about 29ers:
They're faster downhill
They're not as good on very twisty stuff. Follow someone you know's a good rider on very twisty fast single track and you won't be able to match they're line
High front end. However, you can sort this with flatter bars etc
Toe overlap – If you've got huuuuge feet, you might wanna check. Especially if you're using large volume tyres.
Falsehoods:
They smooth out the trail – not in my experience.
M