I've always been using the Wilson Pro Overgrips (White)... you can usually get them at a steal....30 pack for 26 or 25 dollars. Great Price, and they perform better than any replacement grip or leather grip I have used. If I don't have one on, I feel like a N00b...Serious. More than half of the high school team I was on used these white grips cause they last long enough and are grip well. When you start to notice slippage or a darkening color after multiple usages, it's time for you to change it. During my season playing every weekday and saturday, I changed them at least once every two weeks......I was Michigan Division 3 1st-Doubles state champion this last fall season, if that might help "convert" you. hope this all has helped you in your search and game.
Wilson Pro Overgrip 30-pack White.....from tenniswarehouse
http://www.tennis-warehouse.com/descpageACWILSON-PRO30.html
oh michael sendor lol. wow thats wierd you were just in a tourney i played. im 3 singles for parma western btw