I'm definitely a mug guy. I have, and carry, a snow peak double walled mug on every trip. I prefer to cook/rehydrate in my cookpot, and then eat from it, instead of dumping hot water into an FBC meal and eating from a bag. So I heat water first for my coffee/tea, then cook/rehydrate my meal.

I do like to lounge in camp, especially at night, when I'm enjoying a mug of hot cocoa or herbal tea while chatting with camp mates, before finishing off the night with a dram of scotch. A mug is a definite for me, and I definitely prefer double walled - keeps hot drinks hot a bit longer, you don't burn your lips on the mug when you go to drink something hot, and you can easily hold the mug without gloves and such when there's hot liquid in it. Win-win-win! :-)