Palladium Books' Heroes Unlimited RPG is the very first RPG I ever played. Ever since then, I've been a fan. Not to say that the system isn't convoluted and begging for a modern revision, but I think I can appreciate what Kevin Siembieda accomplished with his Megaverse and how he games. Despite its issues, I always come back to Palladium at some point or another.
All that said, the GM Kit for PFRPG is all right. I bought it because I liked what the Rifts GM Kit had to offer, and would likely buy one for HU if they ever produced one. The artwork on the GM reference sheet is shoddy low res images lifted from other Palladium books, but having all the charts gathered together in one place is really what its supposed to do. So I'll forgive the art. The combat matrix is useful, as are the circle references and spell and skill references, but what is lacking is ward references that Diabolists crave.
Overall, a middle of the road product that could have been put together with a tad more polish, but is functional and serves its purpose.