First of all, the novelty of this mug is something I really don't think could wear off, whether you're buying this for your coffee loving self, or as a gift to another coffee enthusiast.
Although a little small in volume for those of us who enjoy a large cup in the mornings, the insulation keeps it hot for ages, long after a normal mug would've gone cold. This, combined with the silicon lid, make it great for morning traffic and other times your mug may be left unattended for a while.
I can't yet comment on the durability, but it feels solid enough to last as long as any other mug.
And again, the design is just brilliant. I can't stress it enough.