^ I've always had issues finding Nether Fortresses. I had to wander thousands of blocks just to find one (no easy task, even when you've got some enchanted diamond armor) - and even then, there's no guarantee it'll have some Nether Wart for you.
And the baby zombies. They freak me the hell out.
Oh, and yes, my FPS often suffers mightily with the latest updates. The zombie swarm is a common culprit.