I've noticed over the years that line-source loudspeakers have virtually disappeared from the (North American) high-end stage. We have Martin-Logan, Sound Lab, Janszen (yes, there back) and Inner Sound for ESL-dipoles; Magnepan and Analysis for planar-magnetic dipoles; VMPS and Wisdom for "boxed" planar-magnetics and Selah, Scaena, AV123 and Audience for boxed dynamic lines. That's all I see. This is an astonishingly small number of co., being that there are at least 150 high-end speaker makers in the U.S. and Canada.
There aren't that many reviews, either. Harry Pearson seems to be the only reviewer who perennially has lines in his system. Robert Greene likes lines...but uses Harbeth monitors as his reference.
It looks like Peter Walker was right - humans can (seemingly) decode sound much easier when it's sourced from a point. And this should especially be obvious to those who are familiar with the sound of live music - which Mr. Walker undoubtedly was......