Been through a few Walmart Specials. However, both of them ended up getting stolen.
They were ok, but over a few months some things get loose that never seem to be able to get tightened down. Out of the store, they typically ride fine.
If you can find a tour bike on CL, I would do so. You will cover a lot more ground on them than a Mtn bike which is nice, even in wind. Mtn bike suck in the wind.
Shimano components are always nice, imo.