Actually, I would take cyclocross out of the mountain category- and I would highly recommend a 'cross bike for someone who rides a variety of terrain. After realizing that my hybrid was holding me back on pavement, I traded it in for a 'cross and immediately extended my ride length (on both dirt and paved roads) by almost 10 miles. The one issue I'm dealing with is that having only two chainrings up front makes uphills harder, but that just means I need to increase my leg strength. With a little customization, a 'cross bike can be an excellent all-round bike. It's definitely a category that deserves attention.
For more detail:
The Case for 'Cross
Wikipedia: Cyclocross bicycles
(Sorry if this sounds like a testimonial. I'm just so infatuated with my new baby!)