Ever since Notch made Endermen teleport away from danger, they've gone from being scary to being giant chickens.
Case in point: Yesterday, I saw an Enderman and wanted his pearl, so I looked at him. He got mad and came at me, but after one hit from my iron sword, he skedaddled far, far away, and completely ignored me. Looking at him again did nothing. I ended up chasing him across 3 biomes (which remember are huge now in 1.0) before I finally got him.
Another case: This morning, I saw an Enderman and again wanted his pearl. I look at him, he gets mad, I hit him once and he loses interest. Several times I would spot him, sprint toward him furiously clicking with my iron sword in the hopes of landing a hit, and when I'm mere meters away, he glances at me over his shoulder with a "Oh, puh-lease" look and vanishes, leaving me amidst the purple particles and saddeningly Enderpearl-less.
How can I hunt Endermen better?