My question is... What's so special about the 2006 OS?

Like what does it hold for us. I don't want to get all excited just because of something not worth my time like one or two new additions (voip, IM client). We need something B-I-G~BIG!!! Is there a difference between a software update and a OS update (in this case)? Also, does this mean we can port it like a regular software update?