Commuter choice for bike trails?
I currently am using my mountain bike that I swapped slicks onto for commuting. I ride the mountain bike trails often, so swapping tires has become a bit of a pain. I am looking to get an inexpensive new or used road bike for my commute. My commute is about 6-10 miles depending on where I park, but 90% of the commute is on paved bike paths. I can shower at work and I wear my cycling clothes on my commute, so fenders are not an issue. I don't need a rack either since everything I need fits into my Camelback.
Taking all of this into consideration, what bikes would anyone recommend that cost between $500 and $1000? Should I go with a used road bike of craigslist or should I go with an inexpensive new bike?