Well, I don't know if they hang out with each other or anything, but they're at least pals, and Williams regularly has Limbaugh on his program, where he's treated with respect and given a good 10 minutes or so to discuss the issues with Brian. The newsroom in Secaucus doesn't become filled with hisses the moment Rush walks through the door.
I've long admired Williams. He anchored the 5 and 11 pm news (I think) on WCBS-TV in New York before getting hired by NBC. He's always had that undefinable "anchor presence," and has always been fast on his feet. There was never any real question from the moment he was hired that he was going to replace Brokaw someday.