Mike is someone that I regularly interacted with on the forums in the days of yore and someone whom I was sorely sorry to see leave Paizo. He had been one of my favorite Paizo authors and was always encouraging, friendly, and approachable when speaking to people on the forums (at least in my experience).
I'd like to add my condolences and well wishes to his friends, family, and the Paizo staff. I only wish I'd had a chance to meet him, he seemed like an awesome fellow.