Post Merger Integration

I was interested to know which areas of Human Capital integration have proved the trickiest for members in the past. In my experience, a lot of challenges tend to come from the merging of compensation and benefits practices. Generally, orgs have different practices, leveling systems, even pay philosophies which make integration very difficult and require a lot of trade-offs in how harmonized the practices will become.

But I’ve also seen programs where the harmonization is quite easy but the systems alignment is very complex and I was wondering what others have experienced as the most difficult area of Human Capital?