I have a different take, but it’s not because I disagree with what others have said…
Mainly, the title of this thread, “…Izotope Neutron? The automatic mixing plugin?” I haven’t paid attention to whether they are really touting it as an automatic plugin or not, but you shouldn’t look at it as one.
At best, maybe it gives you some hints at where to start with some eq points on a vocal. I’ve played with that a bit, and don’t find it disastrous. But I consider this a minor side feature that won’t get much use from me.
I gave it a demo and immediately bought it at the $199 intro at the time. But I never even tried the automated stuff—I never expected much from it, nor wanted it.
I find the plugin itself quite useful and quite good. First, the individual components are flexible, and the fact they come as a collection that can be rearranged, modified, and disabled means that you can put together your own presets for specific instruments and sounds easily and conveniently. The EQ is the main thing and the part I’ve worked most with, but I’ve found the exciter and transient shaping to work out very well for the few spots I’ve really needed them. There are so many compressors (I have so many, you have so many) that I won’t comment there, other than, again, it’s nice to have a couple of compressors in that chain. The EQ is really nice, with the compression and side chaining bands to other tracks and all, and very nice metering.
But yeah, forget about the “automatic” idea.