Yep, I've used them. They work fine inside a shop with a good flat floor. Not terribly hard to push a car around with them and it's not like you are moving it far inside the shop.
I have found they don't change direction well - I have to alternate pushing the front then the back to get the car over to where I want it. Last year I decided I wanted the car turned 180 degrees in the garage - THAT was fun!