We put about 1100 sq ft of New Age flooring in the first floor of our house, including the kitchen, on top of stained concrete slab. The product is very durable due to the stone composite core and wear layer, however it is very rigid. It is not tolerant at all of inconsistencies in the subfloor finish, i.e. bumps, ridges, etc that are more than 3/16" over a 10' span. The locking mechanism is solid once you get it to go together, but it isn't the easiest to work with. For a garage, if you have a gentle slope but very flat surface, you should be fine. The best result will come from putting most of your effort into making the surface as flat as possible, whether that is via grinding or using a self-leveling prep product, or likely both. The prep work is time consuming, but it is what keeps the tiles from popping apart or lifting.
