I bought this mug after much searching because it was the only microwave-safe, non-plastic travel mug that I could find that didn't have a review complaining about leakage. I regret to inform you, that the lack of reviews complaining about this problem is not an indication that it does not exist.
The trouble seems to be that the silicon lid expands when exposed to heat, therefore when the beverage is steaming hot a gap forms between the cup and the lid. This problem is irritating and inconvenient, but the lid fits snugly for the majority of the time that the beverage is of drinkable temperature. I do, however, have some trouble with it dripping due to the sloshing produced by walking.
A far as insulation goes, I microwave it before walking to class (which takes about 15 minutes, in Los Angeles weather, so not super cold), and I find that it is pleasantly warm for about a half an hour after that. I don't know how this temperature retention relates to other mugs, but I thought I'd put it out here.
The volume of this mug relative to it's weight is slightly less than desirable but I think that is to be expected from a ceramic cup. It's grip is fairly comfortable.
This product could easily get a higher rating if the leaky lid design flaw could be overcome.