Looks really cool.
I stumbled over this[1] page recently, which has a method that's apparently is better than the "traditional" Savitzky-Golay filters.
The idea seems to be to start with the desired frequency response, with lower frequencies close to the ideal differentiator, and higher frequencies tending smoothly to zero. This is then used to derive the filter coefficients through a set of equations.
The author generalizes it to irregularly sampled data near the end, so would be interesting to compare the approaches.
Just thought it'd throw it out there.
[1]: http://www.holoborodko.com/pavel/numerical-methods/numerical...