Created attachment 76557 [details]
picture screenshot of gesture, sort of benchmark

I did personnal sort of benchmark , using the last feature 'line smoothing' with my  hardware for both 'openGL' canvas ( Nvidia proprietary driver, 310  ; gfx card : GT220 ) , and CPU canvas ( icore7 2.7Ghz ) . 

The picture file in attachement show clearly the problem : I reproduced the same gesture ( a loop pattern , a squary line , then little cross ) using same parameters for both 'mode' : the result , a big inconsistency : 
- using CPU, the feature does what expected (ex at 100/1000 :  my loops are constant rythm , squary pattern is smoothed )
- Using OpenGL :  it does behave really different, with non pre-visible way to draw ...

Affect also basic-smoothing. 
I couldn't draw in Krita if I had to choose OpenGL , the line result would feel broken here.