Haven't tried hot but cold is way better than frozen IMO. Plus cold more resembles what they drink in the movie; for some silly reason that matters to me, lol.
For someone who's never had it and wonders what it tastes like, the best way I can describe it is butterscotch-flavored cream soda. I've heard it's too sweet, and I can understand that opinion, but I much favor savory food over sweet food and I still thought it was pretty good. I'd never be able to drink more than 1 in a single trip though, and even that one takes me about 30-40 minutes to finish of if I drink it by myself.
I'm definitely looking forward to trying the pumpkin drink next time.