NSPS was an attempt to push towards something more merit based (still pay band structured, NSPS bands spanned 2-3 GS grades). NSPS was rolled back in 2010 or so because the requirement was that everyone had to be on it by 2009 (early 2010?) and that didn't happen.

There are various *demo (lab, acq, I think some others) that are basically the same as NSPS (in principle) and ostensibly merit based. But they're also capped because of the correspondence to GS grades. Pay can increase much faster, in theory, than under GS but also you can be denied any raise except the general pay increase (below inflation, so a real pay cut even if a nominal pay raise) if your performance is poor.