Resting on its laurels
I have stayed at the Ace Hotel in New York four times now, each for several days. During my first stay, I was seduced. Second stay, slightly less so. Third stay, slightly annoyed. Fourth stay, I felt a bit cheated -- thinking "this was not the hotel experience I paid for."
First, the hotel should be applauded for its cutting edge restaurants (and great service in the restaurants too boot), hip lobby scene, and great design throughout (rooms and all). 
That being said, the devil is in the details. A few tidbits which demonstrate my disappointment:
1. Room doors are very thin. One morning two repairmen were arguing for 20 minutes straight before I asked them to quiet down.
2. Room service knocked on my door every morning at 10 am and came back every 15 minutes, even after asking them to come back in an hour.
3. They have cute postcards at the front desk. When I asked them if they could send it for me, they said "Sorry, we don't send mail from the Ace Hotel so there is no way I can send it for you." REALLY? When I expressed my disappointment, the employee didn't really care or the disappointment didn't register or something like that... Hotel employees, especially at hotels this expensive, should notice these things and do something about it. What would have cost the hotel 40 cents now cost them goodwill and a future client.
4. Elevators are slow and often out of order.
5. Front desk knocked on my door at 12:15 the day I checked out to "check on my progress." I know for a fact that the hotel was not fully booked, so this just came as another annoyance when I was already unhappy with my hotel stay. 
I'll stay somewhere else next time.