Originally Posted by cpach

Road bikes make fine commuters if you're accustomed to them. I advice you don't necessarily rule them out if something promising pops up. It depends on what you want--I commute on a a road bike (well, actually a cyclocross bike with road tires), but I also do a lot or road biking, and basically treat the commute like it's some kind of time trial, and often don't carry very much with me.

Potential issues with road bikes as commuters are: many are set up with relatively aggressive positions where your upper body is bent forward, which improves aerodynamics and power output, but can be uncomfortable for some, and can potentially mean it's more difficult to look around you if you have poor neck flexibility. This is variable: some road bikes can be set up with fairly high handlebars, but very few will put you in a very upright position like many hybrids or mountain bikes. I don't think this is a big deal honestly for a fit person, however. Also many road bikes have poor clearance for fenders and larger tires, and on many it's difficult to mount a rear rack should you ever want one.

In the price range you're considering, road bikes will mostly be older 70s-80s "ten speed" bikes with downtube shifters etc. These are fine and dependable bikes, but frequently are needing some love. Are you interested in learning some basic (and perhaps not entirely basic) mechanical skills?

Depending on how hilly your area is, a fixed gear or single speed bike requires less maintenance and may be available for less, although you're still mostly looking used at your (rather low) price range. Older mountain bikes lacking in suspension are also very good candidates for commuting, but you'll go meaningfully faster if you change the tires to slicks.

Mostly you should find a bike (whatever kind) that is more or less the right size for you(http://bicycling.about.com/od/howtor...e_size_hub.htm is an OK guide), and from a quality manufacturer (no Walmart bikes etc) with reasonable quality (even if old) components.