My sister has a comfort / hybrid bike (Trek) and is very happy with it. We just returned from a cross-state ride of approx 370 miles, and she's still happy with it! < she does not do any mountain / off-road riding either - just the bike paths, some commuting, etc >
I currently have a mountain bike (Raleigh M60) that I put slick tires on for road riding (I do switch out the tires for some off-road trails, though). It has served me well on two cross-state rides (470+ and 370+ miles) but I will definitely be looking for a road bike in the next year or two... < just can't quite keep up to the roadies!
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All who joy would win must share it -- happiness was born a twin. (Byron)