Hybrid Bicycles - Used Trek 7.3 FX or Sirrus or Rapid 3?

I'm a n00b looking to get a hybrid bike for commuting and losing weight and improve fitness. The commute to work is 6 miles one way. I would also like to do some longer rides on the wwkend, but have no aspirations of competitive riding. I've been to two LBS, one had a 2009 Giant Rapid 3 that I liked, and the other carried Specialized. The 2009 Sirrus is $499. They only have it in blue (I would prefer black), and not sure if I like the style of shifters on it. Felt fine for the short ride around the parking lot. The Rapid 3 is a nice looking bike, but at $579, it might be a little more than I want to spend considering I will need helmet, shorts, rack/bag, etc.

I also found a 2008 Trek 7.3 FX on craigslist for $365. It has a small computer on it that indicates 90 miles on the bike, and includes a small zipper bag. It appears to be in excellent condition. I took it for a short ride and had no issues with shifting/braking. At this lower price point, I can buy the additional accessories and stay under budget. The obvious down side to it is I don't have a warranty, no initial fitting (unless I pay for one..."free" with the new bikes), and no discounts on initial accessory purchases.

Would appreciate any feedback on the price for the Trek, and any other general thoughts on pros/cons of my options. Hopefully spring will arrive at some point and I can get out and ride!

If a warranty and fitting are that important to you, buy a new bike, by all means. The computer may say 90 miles, but you have NO idea how many really exist on the bike. The sirrus should be a LOT less than that right now, if its the base model. I payed $479 for mine this past summer, but the 2010 models have been out for a few months now, a 2009 is no longer current...meaning there SHOULD be a discount. I have the blue 2009 sirrus, and I like its looks VERY much. But, we all like different colors :)

If money is a concern, the Trek should not be a problem. Being a 2008 its unlikely its going to have any issues. A tune up is all of $40-55 most places, keeping you just over $400. Probably the best deal of them all. Or learn your own wrenching, its easy to tune a bike :)

I will also add that My Sirrus sure is a very comfy bike to ride. I enjoy being on it more so than any other bike I own (although If I could find some single track in my area, My MTB would be more fun...) In the end it is YOUR choice. Take the sirrus for longer than a spin in the parking lot. Spend 15 minutes or more on it if possible. Or, buy the Trek if it fits good and is comfortable. That is a good price for the Trek :)

Fit is EXTREMELY important.

If you have already visited many dealers, and ridden new bikes, you should know what size you NEED! Make sure the used one is the correct size, not just one that will work.

At the end of the day, you have to buy the one that you like the best. One of them will jump out at you as being the most comfortable, and the nicest to ride. It's also important to get the color you like, or you won't ride as much. Can they get the color, and the bike, you want? If not, keep looking - don't settle for less than you want.