I listened at length to the old KLH model 9 electrostatics, professionally set up in a big room, using a state of the art tube amp (at that time). It was ok. I had trouble seeing what the excitement was about. No bass to speak off, either. Like a lot of specialty speakers, I think you get it, or you don't.
I think the thing for many planar listeners is the float, typically in the space behind the speakers, depending on front wall hardness. I find it a little disorienting w planars, but many do not.
I was first exposed to KLH 9s in 1970, a double-pair in a stereo store where I was working. Yeah, you need a sub, though more with some than others. I would not favor a float or radpat like that, myself.
I more recently auditioned a nice big pair of Acoustats, and sometime after big Mags, both in bespoke rooms, and found the presentation similarly odd unless I sat right in front.
The thing that I and many other owners intensely favor w Allisons and dbxes and a few other designs, and what I thought this thread might be about, is 'getting the music up in the air', as Roy Allison once put it. I have known serious listeners (never working musicians, however) who found the scale of my dbx SF1A system simply too much, though.