I think it depends on which person you're talking about: the entrepreneur, or the record maker? Sean "Puffy" Combs, Puff Daddy, or P. Diddy? All of these entities are embodied by one man, but they've all had an impact on Hip Hop; both positive and negative.
The entrepreneur stretched the boundaries of what Hip Hop moguls could accomplish; and how far they could go businesswise and financially, and that's definitley a good thing. The record maker started in the early 90's, and helped broker the union of Hip Hop and R&B that birthed a lot of classic records.
But, the differences between Sean "Puffy" Combs, Puff Daddy, and P. Diddy is where you enter the gray area. Puffy had a feel for music, and helped mold the sound, look and careers of Jodeci, Mary J. Blige, 112, The Notorious BIG and others. And Puffy's instincts made the first five years of Bad Boy (1994-1998) almost epic.
The commericial success of Puff Daddy, however, helped derail New York Hip Hop in the late 1990's. HIs surface-level sampling and glossy vibes prompted a lot of glory-chasers to follow his lead; and it diluted the quality of a lot of records. And when he became Diddy, Sean "Puffy" Combs was gone for good. He wasn't a record man anymore; he became a walking corporation. Artists who thought they were in business with Puffy, like 112, Faith Evans and New Edition, realized that he'd left the building, and the dude they were now dealing with (Diddy) had no time to guide their careers.
Sean's a complicated dude. As such, there's both good and bad in what he's done over the years. But, you got to give him his due. I think he's done more to help the game than hurt it.