I work at a small company (~30 employees) total that's been around for around 35 years. We don't have anyone dedicated to HR, it's just part of the jobs duties for one of the founders. About two years ago I heard bout Zenefits and went through a sales call with them.
The sales guy sounded like he was about 21 years old, didn't know anything, and was a total Bro.
Everything in the call was like "Ohh man, you're still doing it that way, bummer! That sucks man, check this out..."
"Yeah, what we're doing is rethinking HR from the ground up, and we're like Amazon disrupting all those legacy companies out there! We're so innovative you won't believe!!" (no, actually you're just fancy insurance brokers....)
"Yeah man, I hear you, , right man??"
It was an incredible turnoff.
I do think that HR, benefits management, payroll, etc., is totally ready for disruption and a good product, but Zenefits definitely is not it.