In the summer I ride my road bike, a '91 Cannondale 3.0 with 7 speed Suntour GPX, upgraded Ultegra/Open Pro wheelset and an upgraded carbon fork w/1" threadless headset. Obviously drop bars and Bontrager hardcase tires (23mm). It has NO braze ons, caliper brakes and NO room for fenders. It is a true road bike (albeit old) and is fast and fun to ride.
In the winter I've ridden lots of different bikes, but they've always been MTBs. This year it's my '97 ProFlex 857 with XT ders. and gripshift, Magura hydraulic brakes and big fat tires (WTB Velociraptors). It is a true FS MTB (albeit old) and is slow as hell, but fun to ride.
I checked other because I don't have just one bike. I lust for a Surly CrossCheck, but the fundage has not been there thus far. A MTB build on a rigid frame would be about $100-$200 cheaper for me, but less versatile. I hope to have the cash soon, however....maybe from selling my car!