I've stayed here a few times and I really like the hotel. The rooms are very nice, the staff is friendly, I like the pool (and it is isn't crowded) and the spa/health club are excellent. We got massages on a Friday morning and it was great because you get to keep your locker all day so we were back and forth between the spa, the restaurant, the pool bar and the pool ll day (I recommend this).
I don't love gambling here. I mean, it's fine, but I think the casino is a little dark and it's hard to find reasonably priced tables sometimes. But, the cocktail service is usually very good, the dealers are quite friendly and I recently discovered that you can redeem sports book tickets at the casino cashier when the sports book is not open (this is really fantastic). I don't really care for the layout of the sports book - it seems very cramped to me.
I like the variety of restaurants at Aria and its close proximity to Bellagio and Monte Carlos (walk - don't take the tram). I will definitely stay here again.