Like many others, I do not like many of the rules he co-authored, nor the general approach embodied with such things as 'levels' and 'classes'. That said, I do not and cannot deny the pure nostalgic joy of a quick, mindless dungeon crawl...and without him, the hobby we all know and love would have been much poorer. (And, in all fairness, I was able to buy up a whole batch of 1st Ed AD&D books that I never had when I was younger--parental disapproval of the hobby and all that--and was delighted to find that so many things I did not like about the genre were against the designers intent!)
Some time ago, Mr. Gygax wrote a brief article for the Excellent Prismatic Spray, a fanzine that supports the Dying Earth RPG. In this piece he explained the influence that the works of Jack Vance had on his game (guess where IOUN Stones came from). Towards the end, he mentioned that he would be delighted to play DERPG, if only Jack Vance himself could be persuaded to run the darn thing...I should like to think of him somewhere, sitting around a table with Fritz Leiber, Jack Vance, and Roger Zelazny as they have one whale of a good time playing whatever suits their mood.
My profoundest and most respectful condolences to his family and his friends for their loss.