[Porsche-O-Phile]

Yep to that.

Although in grad school I rode (and still have) my early peugeot mountain frame bike that was converted to a commuter bike/hybrid with slicks (albeit wide ones, not skinny road tires), higher (road) type gearing and an aero bar. Also I put rock shocks on the front just to make the riding more enjoyable on Chicago's terrible streets (potholes, cracks, poorly-filled patches everywhere, etc.) Worked fine. That bike was the ideal commuter bike - it was a friggin' tank. Probably weighs 40 pounds but never broke even with me whealing the crap out of it every day for two years. Got me in damn good shape too. One of my "rainy day" projects is to rebuild it and freshen it up with new paint & a few new components.

For training and actual "cycling" I'd say yea - get a true road bike (although they're delicate). For commuting, build one. Don't try to use an off-the-shelf mountain bike for anything other than short-distance cruising or ripping up some single track.