After using VLC again after a while I was astonished by the sound of its sound engine when speeding up and down. It’s better than anything I’ve heard so far. Does somebody more about this project and if they would be willing to implement the algo into a Max object? It’s available als patch/plugin for some mediaplayers, so they seem to be open about spreading their work.
Sorry, I know this isn’t helpful for you but it might be something of note and I mention it only because my experience is quite the opposite to yours (that said, I have no idea what other playback speed changing examples you have heard to compare).
VLC playback at slower/higher speeds is really terrible on my computer. Really, terrible.