I suspect that you just needed to wait for an update.
My Review Page may give you some idea.
I tested it with differnt typefaces too, and found that even smaller values are needed for some fonts. The point is, that getting the side-bearings right is important before you start adding kerning values. If they are done right, you will need fewer kerning pairs too.
Also see my thread requesting a Quick Preview in the Feature Requests forum. I am using an old PC with on-board graphics chip.