If you are just commuting, then you probably should get the Cannondale, but due to other replies, I am compelled to defend the 29" wheel.
Background (go to the next paragraph if you're short on time): I own a Gary Fisher Mt. Tam_29 (2002) -- took a leap of faith (odd, since I'm in the "don't give a rip" category w/ respect to religion). I use mine for XC riding in alpine and desert terrain. Climbing is a dream w/ this bike, and I've ridden w/ FS riders that have been bucked-off on the line I took. We have LOTS of tight switchback terrain in the mountains around SLC, Utah, and my 29er does great. When you first get on one, it feels different, but you get used to it, and then you never go back.
Have to disagree w/ Frey about some aspects of the 29" wheel he mentioned. Sure, acceleration is a little slower, but if you aren't a racer, then who cares? And I imagine getting fork would be a minor headache (as far as I know, only Marzocchi and Manitou make 29" compatible shocks). Actually, if you get the Fisher, I'd be interested in learning how the Manitou performs.
The 29" mtbs are easier to maintain than they sound. The 29" wheel is actually a 700c wheel (29" refers to the inflated tire's outer diameter). Here's what I know about it:
Spokes: My LBS uses cyclocross wheel spokes to repair broken spokes -- they are about the same price as mtb spokes.
Rims: If you don't care about weight, you can use a 32 or 36 spoke 700c touring rim for replacement. If you really care about weight, then go with Bontrager Race Lites after you've trashed your 1st pair.
Tires: You really aren't that limited -- IRC Mythos and Notos are both great tires for hard pack and slightly sloppy conditions. Also, WTB, Kenda, Bontrager, Maxxis, Schwalbe, and Innova make tires for 29ers. I spent US$54 for my IRC Mythos (kevlar bead) tires, which isn't too bad.
Tubes: They make specialty tubes (700c x 52) that run for about US$7-8 a pop, but you can substitute w/ a 700c x 38-45 (I'm running one right now).
Frames: I think Structure is right about rider height. I am probably near the lower limit at 5'-9.5" (~176 cm). But I love that Genesis geometry. It's the most comfortable, confident-descending XC (hardtail) mtb I've ever ridden.
Sorry for the ramble, but I had to defend my bike's honor. Regards,
James