I just upgraded from version 9 to 10 of SpectraLyers Pro and I must say that I am very impressed. The quality and power of the new version was worth the upgrade. I did a unmixing test with the french song «Souvent, Longtemps, Énormément» by French-speaking singer Diane Tell. Regardless of the genre that we like or not, this song is for me a masterpiece of mixing. Recorded at Studio PSM in Quebec in 1981 (which no longer exists), I had the opportunity to listen to the final mix in the very control room of this studio. I unmixed (selecting Best) this song. The result is clearly convincing, except where the electric piano is concerned. SpectraLyers Pro10 seems to have a hard time determining if it’s an electric piano or a guitar with lots of effects. I have to say the task is substantial… The (magnificent) piano in this song is very evanescent and subtle. The song can easily be found on YouTube.
Hey Joss,
I have the same experience as you with Piano and guitar stuff. Often I think that everything else than Vocal, bass and drums ends up on the “other” layer, all mixed together there, with a few bits and pieces on the piano, guitar. I guess its hard to separate piano and guitar sounds from each other. And even hard to find piano and guitar stuff on songs.
I few times I’ve had it working here with guitar and piano stuff, but it rarely works properly.
It’s the same with HitNMix, Ripx. So I guess both programs is equally good/bad here.
But yes, Spectralayers is about the best there is for these spectral AI extractions. I wich that the developers / algorithm guys works more on the piano, guitar and synth stuff layers. I think its very hard to separate these areas, and those instruments often have about the same spectral print, and consume the same frequencies. Plus a piano could almost be sounding the same as a synth. In this area is also strings, which mostly drowns on synth and other stuff on the “other” layer.
But it’s getting better and better by each release 
So they’re moving in the right way.