They have the lowest growth of their industry (granted, they're ~25% of the market) and every company I've been involved with for the last 20 years either uses

They have the lowest growth of their industry (granted, they're ~25% of the market) and every company I've been involved with for the last 20 years either uses a competitor or used to be an ADP customer. ADP is terrible. Paychex, Workday, etc have been eating at their lunch for years and years now. My perception of companies using ADP is either that they're slow behemoths or they still have some niche issue that's keeping them from switching. ADP is also incredibly cavalier with your personal data. As a potential employee I would see its use as a strong minus.