I recently picked up a like-new '99 TCR and think it's great. I've only had it out twice (too cold/snowy) but I did alot of looking around and asked lots of questions beforehand and the Giant compact geometry frames are pretty well thought of from what I can tell.
I think $500 is a great price for that bike... just make sure the frame size fits you. Because Giant only has small, medium, large sizes - you may need to increase/decrease the length of your stem and lower/raise the stem as well.