We had our first experience with an overnight in a Walmart and it was great.
We arrived late in the day (9 P.M.), extended our wardrobe slide just a few inches to get it off the side of the mattress, and went to sleep. In the morning, we walked up to the store, picked up a few things and then hit the road. There was even a Starbucks nearby and my wife walked over to grab a coffee.
Easy and painless.
There were a couple of semis, a Class A and a fifth wheel also parked there (and a guy sleeping in his car).
This was at the Walmart on Grey Lag Way in Lexington, KY.