I own a Rimowa Aluminium suitcase. For me, buying it was about two things:
I insist on hard-shell luggage for one thing - it keeps out spills, takes a lot of beating, you can put bottles of wine in your luggage without having to worry, etc. In this market, even the "cheap" luggage isn't all that cheap, so it makes sense to spend more to get a much studier bag.
Secondly, there's the hassle factor. I don't want to have to run out and buy a new bag every couple of months. I want something dependable that will last a long time and will work as I expect it to. I don't want the hassle of fighting the airlines for compensation when they've wrecked my luggage yet again.
As for dents or scratches on the suitcase - as long as they don't affect the bag's stability, I don't have a problem with them. In fact, I think they add character. As Rimowa says "Every case tells a story." Mine is still reasonably new, but I have seen some Rimowa suitcases that look like their story would be longer than War and Peace