I purchased SpectraLayers due to needing to rip stems from already mixed music and occasionally remove noise from client supplied audio. SpectraLayers does both of these tasks extremely well, one of the best and most capable in my view. Vocals have come out sounding pristine, noise removed very effectively using the low and medium aggression repair presets. The high aggression/max option is much more hit and miss, it does remove the worst noise artefacts, but occasionally the original audio quality will suffer. This shouldn't usually be a problem because you should be rejecting such audio if sent it and if it's your recording, then do another take again.
User interface is fairly intuitive, processing of changes seems pretty quick. Price, I think it's a little steep. It is the best and you do get what you pay for and if you're a Cubase user the integration into Cubase itself is great. I think if it were 50 euro less it would be a no brainer in all ways. As is, I recommend it if you envisage using it frequently, are a professional or you simply need the best capability and unmixing quality. If you only need audio repair ie click removing or noise, then RX maybe worth considering instead.
Highly recommended anyway.