Yes I just bought a Wal Mart bike a few days ago, so I found it funny that I would stumble across this question. Honestly, it really depends on what you mean by "good." Judging from your question about how you just want a simple bike to ride with friends and to school, they are PERFECT.
I mean, I'm not like a freaking pro biker. I just take my bike out in the morning and ride 5 miles on the sidewalks for the hell of it just to exercise. The bike operates well. It gets me from Point A to Point B, it looks beautiful (of course everything looks beautiful to me if the price is low enough), and it's great. Not sure what else to say. If you want a simple bike, it's wonderful. I plan to use this bike for a fun triathlon that I'm doing with my sibling in a few months. My really athletic friend who already completed a triathlon used a Target bike and got a great time.
The only thing that may be wrong with a Wal Mart bike is the assembly of the bike. You might want to take the bike to a local bike store and see if they can check to see if the assembly is right and if anything is loose. They may fix it for you with a low price, but honestly nothing's wrong with the bike itself, it may be some lazy teenager at Wal Mart that just doesn't want to spend a lot of time assembling your bike.
By the way, I bought this bike: http://www.walmart.com/ip/26-Mongoose-Ledge-2.1-Men-s-Mountain-Bike/21191086
$135 and fabulous. I probably wouldn't recommend getting the $88, just because when I saw it in the store they were ugly lol. As for the question, does the $135 bike have more quality and durability than the $88? No idea, the $135 just looked nicer and works well.