Trek 1000, two mtbs and working on a fixie for commuting.
Why don't you just test ride as many as you can and get the one you want? They all have their goods and bads. The only *real* legit reason to avoid any 29" wheel is that you have more variety with 26", but that really isn't a reason.
Why you want or need a 26" wheel is to put on the back of your bike to keep the wheelbase short and the handling snappy. Seriously, most of the handling benefits of the 29er wheel happen at the front.
I have ridden 26ers for 20 years+ and I went to a 29er a couple of years ago. When I got the opportunity to try the Trek 69er I went for it and the ride is unique. More fun than I have had on a bike in a long time. This bike loves to wheelie drop, manual and pop the front over logpiles, roots and rocks etc. It descends like it's endo proof.
The Fox fork is propietary to Trek and Gary Fisher, having a reduced trail that keeps handling quick at low speeds.
First Trek I have ever got excited about. Everyone else that I know of who has this bike is just as enthusiastic about it as me.
I live in Va so its mostly single track and can get hilly mostly packed dirt and rocks. The bike I really want i a trek 69er single speed but its so much money!!! my other bikes in consideration are a specialized rock hopper 29er, a haro mary (29er) and I want to look at the santa cruz chameleon.