The room was beautiful and big, but things were just a little weird. The faucet handles seemed backwards, cords from the hair dryer and curling iron constantly got caught up in the badly placed towel bars, the TV was so far away that the remote didn't work from bed. But a really nice room and comfortable beds.
There is a nice pool with a mixture of sun and shady spots, though the pina colada I ordered poolside tasted oddly fishy and my friends cosmopolitan was simply not good.
The gym is really big (even has a boxing ring), though it is super crowded in the morning. Even if you go at an off peak time you get kicked off the treadmill after 30 minutes. Also the water in the gym tastes terrible.
I stayed at the Aria last time I was in Vegas and though I truly never ever hope to go back, if I do I would probably opt for the Aria over the Cosmopolitan.