Williamson was a superb artist. It amazes me that he was only in his early twenties when he began working for EC producing some of the best science fiction comic art of all time. He is one of just a few comic artists able to maintain the quality of their work throughout a lengthy career.
I'm not the biggest fan of Al Williamson, but I certainly appreciated that he presented high-quality work throughout his career. Some guys lose a step in the later years of their career, but he didn't.
I've been reading his work (and that of others) in the EC Comics archives, and I finally see what the big deal is. The art in EC books is gorgeous... and the extra-large reprinting lets me really appreciate it for the first time. I've really been enjoying Williamson's stories... I'm sorry to hear he's passed away.