Treks are not bad. My first mountain bike many years ago was a Trek. I agree with Jumpr with regards to the fork issues, some guy was just telling me the other day that he bought a Mongoose at Wal-Mart (the most expensive one, $300-400) and he was riding down a paved trail and the front fork broke on him, however, it seems unlikely that the fork will break unless you are beating on the bike. I'm not a fan of the cheap RST forks that the bike has and it really makes sense to buy a bike with a better fork than to drop a few hundred and not be happy with it later, same thing goes with disc brakes, if you want those, you would be better off buying a bike with them, and I'm talking about some decent Avid brakes or something, not the junk disc brakes they have on Wal Mart bikes. If you do ever want disc brakes than you have to have disc-ready hubs and frame so this bike may limit brake upgrades.
Also, a front shock with a lockout is a great feature to look for, you will be glad to have it if you are going to do alot of road riding. This is usually present on decent Rock Shox or Fox forks, I don't know how cheap they come. You'll probably find that the RST fork on that Trek will be pretty spongy and theres not much you can do about it (as far as I know). If you have plans on becoming a more serious rider look for a bike thats at least $400 or up new. If you don't care about performance features then that Trek would be fine. Make sure the bike fits you though. If you are 5'7 or below buy a Small, 15", or 5'8" and up buy a Medium 17" frame, and if you are taller than that you'd want a Large or bigger if they have that. These are just estimates. This might be obvious but bike fitment is important.
The deal breaker for me would be that RST fork. Too bouncy when riding on the road if thats what you are using the bike for. However, for less than $300 you can have alot of fun with that bike. I'd also second the suggestion to use slicks. If you are not going off road the knobbies are a waste. Maybe look for something with a 1.75" inverted tread, for instance. That would serve you well for the type of riding you are doing. Also the l.e.d. flashing lights are awesome if you are commuting, and very rarely do you have to change the batteries since their l.e.d. and super bright to take the place of standard reflectors on the seatpost/handlebar.
Personally I think Cannondale makes some of the slickest mountain bikes, and are handmade in the U.S. The thing that stands out about them is that they grind and polish the welds smooth on the frames. Other manufacturers are starting to do this also. Their lefty and headshok forks are generally amazing. Pricey though. Trek also makes nice stuff but I don't follow their mountain bike lineup so I don't know too much specifics. I bought 2 bikes (a C'dale mountain and a Fuji road bke) in the last two years so I could go on and on about it....
Hopefully that covers it :roll:
Cheers :beer: