Well...the plugin takes a very simple thing, and adds some additional stuff...button for this and that...but you can just as easily drop a bunch of reference tracks into your DAW project, and pretty much the same end result. You just take turns soloing, and there's your A/B.
I mean, the plug is OK...it's just dressing up the whole A/B thing, and maybe it feels a bit "slicker" than loading reference tracks right into your project...so it's a personal choice to get it or not...but it's not doing anything that you can't do without it (unless I missed something in the description).
My biggest reason for not doing that sort of A/B thing with reference tracks...is that I rarely am doing a song or mix where I'm trying to sound like something specific or even where I am thinking about some other song...etc.
Maybe in some very subconscious way during production I might think about some song I've heard...but that's mostly for the general vibe...but I just don't mix-to-match some reference tracks.
I can see how doing the A/B referencing would be helpful if you ARE trying to nail a sound or even complete mix that's already been done before....so again, it's a personal choice if this that A/B process and/or this plug would be of great value.
I know in commercial Pop/Rock/Metal/Country/Rap music there's a LOT of shit that sounds...THE SAME...so it's no surprise that even the top pros are asked to make someone's new song sound very much like song "XYZ" that's out on the charts, and then the need to really A/B against that is obvious.