Yes, it is completely different from the book but Blade Runner is one heck of a movie!! Best thing Daryl Hannah ever appeared in (with her clothes on, that is)--and the character parts were awesome, M.Emmet Walsh, Joanna Cassidy, that Chinese guy, and whoever played Sebastien were all just super.
The actor you're thinking of is James Hong (I think he's actually from either St.Paul or St.Louis), and he's been great in a lot of other films. He was also in The Forbin Project, played a bad guy in one of my favorite Outer Limits episodes, "The Hundred Days of the Dragon", was Tia Carrere's dad in Wayne's World 2, and had a memorable guest role as a posh maitre'd in a Seinfeld episode.
I love to watch Blade Runner, love the look of it all, but it's really bad. :') I plan to get my old VHS of the release version made into a DVD one of these days. (':