Re: mnt bike vs cruiser...
You could also build up a mountain bike like a cruiser,with higher handlebars, a comfy seat, etc. The Rotten Orange build (pics in the photo section) is kindof a cross-breed of the best of both worlds. My bike will be as comfortable as a cruiser with an upright seating position and comfortable seat and handlebars, but will also have the durability and capability to take it offroad when I want to, without fear of it falling apart or damaging it.
The cruiser bikes are definitely cool looking, but for practicality and safety, you really cant beat the modern components found on a good mountain bike. Better brakes, stronger frame and fork.. all this make for a good platform to build on.