I use it all the time as it currently is on Prime manually while the song is playing live, but, as I said, I don’t see why the middle couldn’t reset. It wouldn’t hugely change what I do with it, but certainly wouldn’t hurt to have it that way, either.
Other than making the touch area larger for the on-screen buttons and various other stuff that’s been mentioned elsewhere, something that does need to be dealt with by InMusic sooner rather than later is the inability to change the key in increments while the track is still analyzing or if it fails. The system does not actually require the analyzed key to change key. It’s not doing key correction, after all, but changing it in predetermined percentages. So it could show + or - and the number of increments even if the keys don’t show and work all the same. Ditto for those people who don’t want to see key on screen but still want to change it.
I do not think we need it to remain shifted between tracks, though, as apparently, according to your comment, it does on the CDJ-3000. I would, however, like the key change selection screen to stay up for that particular layer even after I’ve left that layer or gone to the browser and returned, though… at least when it’s still the same track. I’m fine with key resetting and the key change selection screen going away on track load.