I think I should add more details about this release.
The main goal was quality improvement and artifacts killing. So comparing to SVP 3.0.x (and MVTools libs):
- no need for frame padding, motion vectors are very accurate at frame edges
- new cover/uncover mask => almost ideal frame edges with 21th "SVP shader"
- much more accurate scene changes detection
- much less "window blinds" artifacts
- adaptive rendering mode that uses more source frames in fast/hard scenes
- floating point calculations in gpu mode => the result is better that MVTools with pel=4
- many tweaks/changes in motions vectors search
- blocks comparison by SATD is on by default ("dct=5" in MVTools)
- bicubic vectors and masks interpolation in the next 3.1.1 version
Overall performance at default settings should be the same as in 3.0.6.
Note that in SVP 3.0.x (and MSmoothFps function) resulting pictures in cpu and gpu modes was exactly the same, but in 3.1 gpu mode can (and will) produce a way better picture.
Also "Ambilight" is really cool in some situations SubJunk
"old, less-stable code" is the latest official Avisynth release and "new and more stable" is in alfa (not even "beta") stage. Also you should know that I've already provided a workaround for 2.6 o_O