For what you spend on a Next, you can get a good quality used bike. Name brand bike frames are generally made of stronger, lighter materials and the parts are of better quality as well. Sure, you can keep an x-mart bike going for years and years but it'll be heavier, uglier, require more maintenance, and perform poorly compared to a 10 year old bike shop bike. I'm all for being a cheapskate, but I'll take my old Trek (13 years old), Miyata (14 years old) and Maruishi (29 years old) over some brand new department store boat anchor any day of the week.

Edit: The Trek I bought new, but the other two were purchased for less than any Wal Mart bike. Other than tires, brake pads, and a couple of chains, the Trek has never required any maintenence. The other two bikes have needed nothing beyond the items I replaced when I purchased them.