I may be mistaken on this experience being WalMart brand -- but I did get a cheap bag of Charcoal at WalMart once for use with some BBQ chicken.
The coal I got did a decent job of holding temperature and cooking for a reasonable period of time. My biggest issue with it was getting it to light which after about 10 minutes I decided was way behind schedule and heated it up with some extra lighter fluid and another match.
Other than the issues with lighting it, I don't recall having any problems with it. I've not tried a long smoke or anything with it though.
In use: Chargriller Pro w/ Firebox | Ugly Drum Smoker (BPS Style) about to enter the fray