Ok, I know, most of the time I DON'T use my road bike for my commute. Why?
-Evil potholes from the awfullest streets in North America (or close): we have poorly maintained roads here in Qc city, mostly because of the low density of population in the province of Qc, and also the abundance of freeze/unfreeze cycles before/in/after winter. Add overcrowded city buses (my main commute route is along the most crowded bus line - which I take in winter), heavy traffic, the "plaster syndrome" (repair? Oh, we'll only patch it now for 1km, it will be okay for a year or two)... well, you get the idea. But I like that road: I'm early on it, and it's the most direct way. And personnaly, I prefer to wait at lights (few of them I have to wait for) than make five dozen of stops when cars blow through them to be faster than you.... So with 1.4" slick tires I feel fine to smooth the bumps
-Hills! Did I mention Quebec city? It is not that bad (only a 100m in 1,5k at the beginning, rolling hills to get to work afterwards), but I live in the Old Port, and everywhere I have to go, there are always climbs to make. So I like to have plenty of gears, if I don't use them much when I'm fresh, maybe after a big, long, hard day of work/errands (remeber: hills everywhere!)/training I'll be glad to have them! -Loads: I'm working and studying full time, training in cross-country, ice canoe racing, rugby, and a rugby coach. That means I need often two set of sport gear plus my work clothes plus my books. Sometimes I have to pick groceries.... My older steel MTB has rack eyelets, so I carry panniers (or a rackpack) for clothes/shoes/balls/PFD and my BIG messenger bag for books/lunch/stuff.
-Love? I love my old RM bike, I have shared many many adventures with it and continue to (like riding in a thunderstorm with 130 kph winds, hail and 2ft of water in the streets two months ago)... should I say more?
-My road bike is an old salvaged bike with a 6 speed cassette: I'm working on it presently. I like it for quick shop stops, grabbing an ice cream in town, going to the movies... I like to move faster when I don't have everything to move with me.
-My other bike is a mountain bike that I use almost exclusively on trails, but I like to cruise around town and in the city parks with.... very very very rare commuting machine. That said, I guess my next buy as a bike will be a 'cross rig with some commuting capabilities: to race cross, train on the road a little more, and go fast with a load (it'll get less of a load, I'm almost done with rugby and grad studies) on the streets. But I don't think I'll go SS for a little while :-p