If you can believe it, I actually road a Trek 720 Multitrack on the Pacific Coast route from Seattle to San Francisco about 10 years ago. I really loved that bike. I was doing solo, self-supported camping tour, carrying around 45-50 lbs of gear on the bike. It held up remarkably well considering that none of the components were exactly high end. The only problem I ran into was a couple of broken spokes on the rear wheel on the second-to-last day. So based on that, I would say that a 700-series bike would probably be a decent commuter bike if it's in decent shape; it'll probably hold up reasonably well. The high end of the gearing is low, but during a commute how fast do you really need to go?