Specialized makes nice bikes. My road bike is a Specialized, and one of the mountain bikes I'm considering is the Specialized FSR XC. The lower end bikes usually have a weaker fork and brakes, but for someone as light as you, that won't matter. For someone like me, well...

Did you ride it? Like I said before, the most important thing is how it rides. The frame is a decent frame, so if you get it and like it, you can upgrade the parts later. Although I'm not one of these guys who upgrades everything just for the sake of doing it (with bikes, anyways). I ride it until something breaks or gets worn out, then I replace it with something better.

There are a few things I would recommend getting right off the bat if you plan to do any serious riding:

1. a seat pack

2. spare tubes

3. tire levers

4. a pump

5. a helmet - yes I know a lot of people think helmets look funny. But, think of how funny you'll look with your brains splattered all over a rock...

6. biking shorts - you don't have to get the spandex ones. They make them that look like regular shorts. Your butt will be the first thing that hurts you. A good pair of shorts will be a very worthy investment.