Personally, cliffhangers annoy me. Especially if the sequel isn't coming out any time soon. For me, I read so many books that by the time the next book comes out, I've essentially forgotten the cliffhanger and am left confused when I start the new book.
Or, even worse, I spend the intervening months with a vague worried sense of unease about what's going to happen to those characters.
Still, it is an effective way to bring readers back in a series.
So, what do you think? Do they piss you off or do they leave you panting for more?