I'm closing in on purchasing one of three mountain bikes from an LBS: a 2010 Specialized Rockhopper Comp 29 Disc ($760) ; a 2010 Specialized HardRock Sport Disc 29 ($569); or a Cannondale F7 Hardtail ($618). I'm accustomed to riding a hybrid or road bike. I test road all three and honestly I did not feel a huge difference between them (although I must admit my test ride was around a parking lot).

What do you think of these three models? What about these prices? Will these models stand up well to light offroad and some single track? Are they the kind of bikes I might quickly outgrow, or are they all solid, durable bikes on which you could later add upgrades if necessary? I welcome your ideas. Thanks!