Build quality aside the greatest aspect of this mug is the thermal performance. I have filled my mug in the morning at 7:00 a.m. with hot coffee and still had a pleasant drinkable beverage by 4:00 in the afternoon. I haven't done a scientific measurement, but when I filled the mug with ice water 24 hours later there was still ice left in the mug. I don't know what kind of strange witchcraft they are using to get this level of performance, but bravo!
The only significant downside I have found is cost. This mug is easily 4x more expensive than your common travel mug. That being said, for no-spills, hot beverages, and a reliable design it's easily been worth it for me. I've had it for almost a year now and it still looks as good as the day it came out of the box.
Update - May 2017
I've been using this travel mug for almost 18 months now on a daily basis and I can honestly say it's the best one I've ever had. Almost no wear and tear is showing on it, the seals are all intact, and the mechanisms all work the same as they did the first day. The only absolutely minor issue I have encountered is a small leak that can sometimes appear at the front of the mouthpiece but that is not a fault of the mug. If you don't clean the inner seals regularly (once a week or so) you can sometimes get build up under the o-ring which causes a seep. A quick cleaning and everything's back to normal. Cold or hot, this is my go to mug and has a place of honor on the side of my backpack.
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