Old news, that's been up there for a week or so.
But yeah, they're pretty standard as far as role goes, doing exactly the same thing as ITs, but they're far more versatile now. Have you seen how quickly a Zergling becomes a Baneling? The cocoon phase is like, 10 seconds maybe. With Zergling mobility, you can get Banelings just about anywhere, and they're way simpler to attain than ITs ever were.
"I want kamikaze dudes...let's tech to late Tier 2, assault a Terran base, and leave the CC just alive enough to infest and start slowly pumping out weak little walking pusbags."
Having quickly manufacturable suicide units that you can spawn in almost limitless numbers is almost ridiculously good. Banelings make me fear playing against Zerg.