The other option is to find a used MTB that is in your price range, maybe a bit beat up, but is of a decent caliber. I've seen so many used, but almost new bikes for sale around here because a young couple bought matching bikes to do "together time" biking, then decided mowing the lawn on Saturdays was more important. If you find a used bike from someone you trust for a good price, post the specs (including the size and your height), and I'm sure the folks here will help you decide if it's a bargain.

A note on dept store bikes. I bought a Huffy MTB (sic) several years ago, alum frame but no shock. The first ride the pedal fell off and stripped the crankarm! I got it in a different town from where I was staying, and the local K-Mart wanted to ship the bike back to the factory for the repair, taking several weeks. I went to a local bike shop and got a new arm for $5. However, after that, I put on slicks and the bike has been great for tooling around town. I still wouldn't take it on trails, though!