Treebound, thanks for the response. January 2011 -- Manufacturers can no longer manufacture products with the pre-2010 grooves and can no longer ship products with the pre-2010 grooves. Retailers can continue to sell clubs shipped to them before this date as conforming clubs indefinitely. This is a fact.
When you are comparing fairway shots with new vs. old grooves there is NOT supposed to be any difference because there is no grass between the clubface and the ball. However, shots from the rough are going to be affected. So, if we are both 8 handicappers and I am using the pre-2010 grooves and you are using the new grooves, I believe I would have a clear adavantage making better contact with my ball in the rough than you would. Better contact makes for a better shot.