I only encountered him personally once, on a panel the first time I attended a con (Dragon Con, 1988 or so?). I thought he was an arrogant jerk. I’ve heard from others that he could be quite nice, so maybe it was some kind of schtick. I did enjoy all the Thieves World books, despite their unrelenting darkness.
He was scheduled to be at MarCon this weekend, so it seems his death was sudden and unexpected. I wish the best to his family and friends.