Hello all. Long story short, my Raleigh Cadent was stolen a few weeks ago and I now have around $600-700 to spend on a bike. I have a few questions and would love some input. First, my situation. I commute 3-4 days a week year round, 8-15 miles, carrying whatever I need in panniers on a rear rack, and riding often in street clothes. It would be nice, but not necessary to have a bike that could also handle hard-packed trails and such on the weekend. It is also essential to have a low-maintenance bike, because I am not too handy and cannot afford bike shop repairs very often. I don't have a strong preference between a road bike or hybrid bike, but road is what I am used to and I like to ride fast. Last important detail - I have my mind set on the $1000-1500 MSRP bracket so I need to get a deal.
So my first question is whether I should cruise Craigslist for a bargain 5-10 year old bike, or venture online to a seller such as BikesDirect. I am not entirely opposed to putting something together, and I like the idea of a new bike. However, I think I might be able to find a higher-end bike in the used category. For instance, I found one guy selling a 2000 Lemond Buenos Aires for about the right amount.
My second question is to what extent these fine distinctions matter between touring, cyclocross, triathlon, and commuter bikes for my purposes. I am aware that these are different in some respects, but I mean, isn't a bike a bike? Bear with me, I'm relatively uneducated and don't have a ton of time at my disposal right now to educate myself.
Thanks for the help!