Have stayed at Gritti, Danieli, Bauer, and Cipriani, but not Aman.

Favorite by far was Cipriani. Very, very easy to get to St. Mark's Square, and for me the ability to get away from the hustle and bustle of Venice was really nice. Beautiful pool and tennis court. When I was there, the food was outstanding, but another poster reports that it's not so great anymore. The room we had was fairly modest but nice.

Would probably try Aman on my next visit, but to be honest while I don't mind paying high prices for a resort, when I'm going someplace primarily for sightseeing, paying a huge amount for a place to sleep somehow seems like a waste of money.