It's not the idea of them that I dislike...I thought it would be a cute and fun thing to have for the site when it was first announced. The execution, though...the linework is just too thin for my taste.
They don't really feel 'iconic' in the way that normal emoji's do; many of them have fine details that you can't even see unless you look closely. Which kind of defeats the purpose of having a little icon that's supposed to portray how you feel at a glance so you don't have to write it out...
The dog emotes were the biggest disappointment...I'd much rather use the original source pictures than the end result...