I used too up until last year. Stopped doing it and I can't tell any difference nor any vibration, like someone said above I don't think it's a major issue on commercial machines, plus if a blade is really dinged up bad most LCO's just throw it out. I've used the little cone thing pictured above and it's not accurate, I've had blades with huge chunks taken out and the cone showed it to be perfectly balanced, and visa-versa. Same thing with the nail in the wall trick, probably a bit more accurate but not worth the time. Unless you want to spend $150+ will you be able to get an accurate balance.
Up North Yard & Drive