I have two decks on the front and back of the house that are composite... one 12'X50' and another 15'X12'. A third will be added next year. I like the stuff on a deck, but I wouldn't advise using it on a garage floor. I live in high desert so I don't have the mold problem, but I did notice it is discolored by oils. If someone drops a piece of meat, etc., it will stain the composite surface. It does come out with time and some cleanser.
There's no way I'd install it on the garage floor. I'd spill oil, transmission fluid other assorted chemicals. That would be bad enough... but then dirt would fill up the cracks and be a pest. Don't even get me started on the possibility of it denting when you drop a tool, drag a piece of lumber or metal over it. I find it mars when treated roughly. I don't part my chained up lawn tractor on the deck... I'd like to, it's no fun hand shoveling 4' of snow off the deck. Even my tracked snow blower's pads could mar the surface.
The stuff is just not robust enough for a garage floor. I'll take concrete any day.