RIP. He was a nice guy and a great artist, but the last years he was quite disabled by (I think) a stroke and it was almost impossible to talk to him. My friend used to visit him to discuss work they did together and I went with him one time; he talked a few times with him after that stroke but it was never the same. I was a big fan right after I saw Alien begin 80s and it was nice to meet him while he was still producing art.
I was a big fan (had been since I first saw the images for Alien as an 11 year old in the UK), however my wife (who is Swiss and knew his son, apparently) is less of a fan of him as a person. I'll spare the details (since, in the interest of fairness I cannot remember the whole story accurately and would not want to mis-represent it in this forum) but yes.. like most people he had his less than perfect moments.
But this should come as no surprise to anyone who's lived a bit. One can be well respected for ones art, but be less respected (in some quarters) for how one acts.
Regardless, I am saddened by the news. It is a great loss IMO.
Very sad, I did not know he was disabled recently. I remember reading a lot about him in the 80s as well, and seeing what he did outside of his work on Alien. Dark Seed (the game) also comes to mind.