Santa put this item in my stocking this year, and I LOVE it. It's got a nice capacity (14 oz), it handles loose tea as well as tea bags, and it really does a great job at keeping the the liquid hot. It's got a very comfortable hand-feel -- the green part is slightly rubbery, so you don't feel like you'll lose your grip, or get burned. The top is very easy to drink out of.
I agree with the previous poster that it's very hard to gauge how hot the liquid is. And removing the tea infuser can be a little tricky at first because you have to remove the top of the mug, run cool water over the infuser, then turn it to remove it. But then you've got lovely hot tea for a good hour, and nice warm tea for an hour after that! I especially love it because I often make a cup of tea and then get busy on the computer and only get time for a sip before I get distracted and it cools down. Not with this thermal mug! It stays nice and hot.