I do enjoy this mug! It does keep my beverages cold for quite some time, especially with ice. Not quite the 48 hours like it claims, I'd say by 36 hours it is chilled, but not cold. My only complaint is that the small hole that allows air in while you drink is too small. It makes the liquid come out too slowly for me.
The smug has good temperature retention but the problem lies in the lid. The lid pours way too slowly so if you're looking to drink a lot of liquid quickly, ditch the lid. No other complaints.