I’ve seen the benefits side being a hurdle, or at least a part that was tricky. Both companies had good 401k plans and health care programs, but each company had its own specifics, and employees appreciated them, they knew these. No side wanted to give up on their specific plan(s). It took a couple of years and gradual alignment to integrate the benefit plans. it was good change management though – they listened to one another and considered the perspective, took the time to align and communicated clearly, transparently and consistently.