For the kind of riding you describe, i.e., mainly urban, a hybrid bike with 700C tires may be a good choice (e.g., the 7300FX). A mountain bike with a front-suspension would probably be overkill. If you choose a wider set of tires on the hybrid, say 35-38mm, you will get a bike with fairly comfortable ride that should be able to handle most of the urban hazards you throw at it. The component level on similarly-priced bikes should be fairly close, so you will not be making a huge mistake if you pick the Marin vs. something else. If you want to look at hybrids with 700C tires, the following may be a good place to start:

Marin Larkspur
Trek 7300FX
Gary Fisher Nirvana

Marin Muirwoods is steel and has MTB tires (26") compared to the ones above that are aluminum and have 700C tires.