I just put up 8' of the cheapest white cabinets from ikea in the garage on the household goods/sports equipment side. I'm happy with them, but I'm not sure if I'll put them on the other side of my garage where I keep tools and car parts. They don't seem like they will be the strongest of...
A little more googling would show you that the hardness is only a few thousandths deep, if that. The increased hardness is really only a benefit for abrasive wear and galling type issues. It won't do anything noticeable if you're dropping a part on the surface.
I've had them in my enclosed trailer, and they are nice. But they are pricey and they are more designed for holding what you need at the track, so they don't have have a ton of storage. Can't say I'd use them in the garage.