If tech talk is off the table, that's all I have to offer.
@audiokinesis: I think the technical aspect of the ESL is quite important.
The Beveridge lens revolutionized how ESL's sound, especially as it applies to sound dispersement and I'm not sure anyone realizes this but per Roger Modjeski who worked for Beveridge, Harold Beveridge designed these speakers to be placed on the side walls (Duke - recall that RMAF show where the room I was working had the speakers on the side walls - that guy whose name now escapes me worked for Beveridge too and copied the concept using dynamic drivers). The early Janzsen ESLs were also quite unique and the Soundlabs speak for themselves.
Having learned a thing or two from Bev, Roger Modjeski designed his ESLs to have uniform sound dispersement, without curving the panels. In addition, he realized the inherent weakness was in the bass and designed his speakers to be bi-amped with dynamic woofers which he selected to work best at 100 Hz and below. We modified a set of my Acoustat Model 2's using one of his panels (actually a half size version) to go along with the stock panel. I use a 4 box woofer array along with the Beveridge RM-3 crossover to filter the highs and lows at 100 Hz (4th Linkwitz-Riley 24 dB slope with a unique passive EQ added by Roger on the low pass board).
The other major tech improvement we made to the Acoustat's was removing the interfaces. Inherently, Roger felt the step up transformer is the real issue with ESLs. Anyone who hasn't heard an ESL with direct drive amps hasn't really heard what they are capable of. I'm working on taking my ESL 57s in that direction as well. As an aside, and from my perspective I do think the ESL 57 is still the standard by which any ESL is judged (it's what Roger Modjeski used as the model for his ESL), especially when it comes to the mid-range, but I also think people underestimate the bass in that speaker.