I always use mic as the noun (mic check) and miking as the verb (miking the drum set). I guess because subconsciously I would say "micing" as "missing." We have a director who always spells it as "mike" and it drives me crazy.
Always have and probably always will use mic. I remember back when I played Kirby Nightmare in Dreamland on the Nintendo. There was an enemy called Mike and for his attack, he screamed into a microphone and if you were near him you got hurt. Man, that was the best game ever.