I would say if you are looking to get in XC racing or just trail riding for fun I would get a hardtail (or a crazy SS Rigid if you are into self mutilation :p), or one of the short travel super spiffy carbon full suspension bikes. If you ever plan on doing Enduro racing or more technical trails, or don't like having your butt pounded for miles don't even look at a hardtail. Again, unless you plan on doing the drops at Santos, no FS bike is 'needed'. A long travel/slacker front/hardtail I feel is the perfect FL bike or something like Trek's Fuel Line or the Slash being the beefies thing you can get away with riding in FL.
To Scott: Slopestyle....that is all....