I'm new to the 29er thing and have just built up a Zion 737 with the same fork (Black OPs) and Geax tires (on Blunt rims).
As much as I love the Zion's ride, I find the frame quite flexy - especially under power. I was originally eyeing the Mamasita but wanted to start with an affordable frame until I determined (rigid) 29er was for me. I also wasn't sure how laterally stiff the Mamasita actually was.
As for the Geax tires, they're my first real 29er tire (ran a Bonty 1.75 and Ritchy Zed on my flat-bar cross bike for awhile) and these things rock! They remind me a of a beefier Hutchinson Python. Mounted with 26" Michelin latex tubes and the wide Blunt rims, I'm able to ride at 25f/27r psi despite my 184lbs weight. Even at those pressures the tire's sidewalls still resist rollover and yet manage to absorb a lot of the 1-2" stuff.
Captain, you don't miss the outside chainring guide on your 1x9 setup? I've tried a few weeks w/o one and have droped the chain several times to the outside despite the tight chain (not really the case in the smaller cogs though) and SRAM X9's super short cage and 3rd eye inner guide. My flat bar CX has the same setup except with an outside chainring guide and I have yet to drop the chain in over 9 months. I have ordered a Salsa Ring Dinger for the 29er.