Gone at the age of 91. Hard to complain about that.
I was never a huge Farmer fan, although I the Riverworld books back in the day. Probably his biggest general contribution to modern media, though, was his creation (as far as I know) of the whole multiverse thing, the idea that zillions of fictional characters in fact lived in the same universe and were inconnected in various ways. Without his pioneering work, we might never have gotten that episode of Nightman were Simon McCorkindale returned to the role of Manimal.
On the other hand, if you thought Heinlein got weird with the sex stuff–and he did–Farmer was if anything even weirder. I still remember his book where his very thinly disguised analogues of Tarzan and Doc Savage had a cock fight (and I mean that in the most literal sense) above a gorge.
Still, one of the great names of what was probably, what, Sci-Fi’s Silver Age? His family’s solace, I’m sure, is that his books will live on after him.