pirate jim et.al. -
c'mon, that's every year marketing hype, you shouldn't be fooled by that and make the leap to counter weighting. if we bought a new driver every year and increased 15+ yds, we'd all be hitting it 500 yds. by now.
first off, they're searching for more distance by repositioning the center of gravity in the head combined with lighter and longer shafts to increase club head speed. plus your talking drivers vs. irons and they're different.
for irons - the benefits of counter weighting come not from just adding weight, otherwise 60g would be 15x farther than 4g by that logic. it's beneficial because when fitted properly, in enhances and increases hitting the ball on the face, thereby greater ball speed, less dispersion = longer distance.
besides, why be a skeptic when it's so easy (and free) to test it for yourself with a trained and reputable club fitter. since most people probably subscribe to a "prove it to me" type of theory, if it doesn't work for you, don't do it. i've been fitted for it three times in the last 5 years and each time it's proven beneficial (and the same weight). with different clubs 2 of the 3 times.
just find a fitter who has trackman and/or flightscope radar. take your 6i and hit 15-20 shots with no counter weight, that's your baseline. then do the same with 4, 6, 8 and 12 gram counterweights. compare the average data of: club head speed, ball speed, distance, angle of club face at impact and dispersion, etc. if nothing is better than your baseline, it doesn't work for you. if one of the weights improves these numbers, put them in. it's that simple.
for me personally, the optimum weight produces much more consistent square face at impact, 2mph of club head speed, 3-5mph of ball speed and 3-5 yds of distance. on the course it translated to more consistent distances and the misses were much closer to the intended line. therefore, more confidence overall
my fitter does this for free, no change, no charge. if there's a change, he only charges for the weights and installation and not the fitting. seems like a win to me.
lastly, two of the best ball strikers ever readily admit to using them, nicklaus and sergio garcia, so there just may be something to it.
just my $.02