If you are thinking about buying a new bike, keep one thing in mind;buy a bike that fits you and your riding style. It is easy to get caught up in all the hype that goes along with new bikes.
Do as much research as you can before you go into the bike shop. Do not be afraid to ask questions, and be honest with the salesperson about the type of riding you plan to do with the bike.

Look at rivbike.com for some enlightened reading on bike fit and function.