Looking at it from the US side, I can see its downside. Cars are cheap. Gas is [relatively] cheap. But, parking may not be, and if you don't need a car, it's a hastle to go to some rental place, as they're much less convenient than the locations for these cars. A quick hop to Home Depot or Wal-Mart or whatever...it's a good thing to have.
Now, flipping it here to the UK, they make much more sense. Cars are expensive. Gas is expensive. Insurance is stupidly expensive. Parking is non-existant. It's a much better option and much more attractive. How, the ones I've got have been hit or miss. Some have been perfect. A lot, not. Broken (and repaired) door glass (which would barf glass every time you'd close the door). Missing body pieces. Gouged tires. TPMS not working. Disgusting windshields. A gallon of 80 yo lady perfume. Missing side mirror caps...and other dents, dings, and scratches.
Maintenance is another thing. To your point, some of these cars take a pretty good beating. I don't know how they follow up with previous drivers that cause this damage, but if I were them, I'd cut them off. It also takes quite a bit of time before they address these things. The more severe, saftey issues are taken care of immediately, but cosmetic and other misc things can take months to get fixed. And, as in the glass, sometimes half assed.
I like the service, but their selection is spotty. They have BMWs here (Audi's in the States) and they're far and few between unfortunately. I'd prefer them over a VW Polo any day. The new Golfs though aren't all that bad. They also have a 320d here as well.
