To improve the timing, go to edit->user settings->show advanced settings -> feedback and then turn the four sliders up to make them more lenient. I found that I really needed to turn the minimum correct / absent ms up a fair amount. I think that this second pair controls how lenient it is for late notes, and the first two control leniency for early notes? Not sure, and the "click here for more information" button doesn't work. Playground sessions would do well to at least figure out some more informative names and make this setting more visible, not behind "advanced settings".
The problems here are probably just due to latency between the keyboard and the program, which probably varies a lot between computers and keyboards. The real solution here would be to have a calibration where the user was asked to play quarter notes as precisely as they can for a minute, and the software can use that info to figure out the latency in the system and use that to adjust these numbers internally. Guitar hero does things like this, for example, with the strumming.
A place to discuss Playground's main curriculum, the Bootcamp.