honestly i swing about 70% on irons and maybe 80% on my driver. i average 260 off the tee and 150 with an 8i with this method, which is plenty long for what i need to do. but my ball striking suffers greatly when i swing an iron more than about 80%, and a driver over 90% is always a pull slice.
i guess i wanted to figure out if my percentages are low, i.e. i need to learn how to control a faster swing. i can swing faster, i just can't control it. if the pros are swinging 90% every time and controlling it, i'd say i have some work to do from 70%.
I watched a video of a Tiger Woods clinic and he said he swings about 80% each time. Usually if he swings out of his shoes at 100%, he does lose some form or balance and it's pretty obvious when he does. I think instead of putting a percentage on it, just swing at a speed/tempo that's comfortable for you. I like what zipazoid said about carrying 14 clubs and the reason behind it. You don't have to muscle a certain club when another club in the bag can do it just as easy with the same swing.