We like pretty much everything about The Cosmopolitan - location, ease of access, rooms (especially nice balconies that most rooms have), friendly staff, good choice of restaurants and bars on property, check-in process is usually much quicker than most other Vegas hotels, quality of room service food is pretty good and they always deliver faster than the time they give you when order is placed (even though it can be an hour during busy times, which is understandable for property of that size), etc.
This time was the first time we had a little complaint. Our minibar was refilled first day after arrival and then for 3 days no one showed up to refill it. Even after we called and requested a refill, no one showed up. Not a huge deal, nothing that would stop us from coming back, but it slightly annoyed me at the time.
On a positive note, this was the first time we tried to ship some packages to FedEx office/business center at The Cosmopolitan and the process was seamless. I know this might not be very important or at all relevant to a lot of people, but it is very important to us and I am happy to add it to the list of reasons why I would stay at The Cosmopolitan again