I have the success with it that I expect to. I've turned some singles into doubles, doubles into homers, and hits into strikes or outs. You have to be smart about when you use it so you don't do more harm than good, though. If I have a runner in scoring position, I don't need an extra base hit to score them so I do not use it then. I might think about using it when way ahead in the count and with the right kind of hitter. I do not use it on guys with big power ratings who are already strong enough to get it over the wall by themselves, there is no benefit. Especially if they are low plate vision guys (meaning they will whiff a lot). Adam Dunn is the most extreme example, Chris Davis comes to mind. I try to use it on guys with high plate vision and average 15-20 HR power as they will benefit the most. Guys like Yonder Alonso, Alejandro de Aza come to mind. As a matter of fact, de Aza hit one for me yesterday on a power swing putting a hanging curve into the RF seats for a solo HR with 2 outs.
I use Nomo's sliders pretty much. I might have made a small adjustment here or there but his manage-only sliders fit with my classic pitching/timing hitting play.