The bearings aren't of high quality, and over time are going to be more prone to failure. Same with the brakes. Give it a good going over or have the shop go over it if you aren't completely sure what you are doing. Those bikes are often put together by people that don't really have a clue and that's the most dangerous thing about them. Another issue could be tire seating...again, poor assembly. That could be tragic. For what it's worth, my daughter ended up with a "bike shop" bike last year when her Roadmaster blew a freewheel. It was one of the MTBs from Walmart. We had the honor of having Koffee Brown in town, took her for a ride, and my poor daughter couldn't ride her six month old bike due to a mechanical failure.