I have a Specialized Hardrock Sport that I picked up for $350 back in August of '06, right when the '07 models hit. I can honestly say it's worth every dollar. Is it perfect? By no means, but I've put 700+ hard miles on it since, and it hasn't flinched. Only things that are different from stock are the tubes, got sick of getting flats on the trails

.
Basically, it's a great bike. I've beat the tar out of it, and it comes back for more. In fact, I've been neglecting it a bit lately in favor of my shiny new Trek, so I think I'm going to get it out on the trail today for some more abuse.
Are there much better? Certainly. It's heavy, some of the components are low-end, and the fork kind of stinks. However it rides nice, has a great saddle, and is bulletproof.
Anyway, I suggest checking it out. YOu may want to swap out the stock tires with something like the Conti Town and Country, but beyond that it's hard to beat. I know it lists for $399, but most shops here are selling them around $350-375.