The first listening was done obviously with the prototype boxes, so I knew pretty much what to expect in the final boxes.
I expected improvement due to:
more stiff, more rigid and dead front baffle
more stiff and dead bass box
better (much better) wiring
better XO capacitors
better XO execution, paying attention to all joints, to directionality of all passive elements (orientation the same in both channels) and directionality of internal wiring. All wiring is of identical lengths in both channels.
More careful box stuffing (rockwool instead of cheap foam).
Closer spacing of mid, tweeter and mid bass
better cable terminals
improved XO layout
improved XO slopes and points for the tweeter.
Re-sized woofer box resulting in more pronounced bass.
Closer to the floor bass positioning, resulting in further reinforcement of the last 2 octaves, compensating for sealed box natural roll-off.

The listening impressions:
The result exceeds my wildest expectations. The sound is better than the sum of the expectations from these great drivers taken separately.
The sound is very well united, not only "for a four way" but for any speaker. The question of integration DISAPPEARS. It makes no sense. There is only music, no trace of driver sound. Lack of coloration, distortions, vibrations results in the drivers reproducing only the wanted signal plus none. The original event is re-created with absolute perfection.
The disappearing act is first class, best I ever heard in my life.
The sounstage depth is equal of that of P-7. Very deep and stretching from just in front of you to some 15 meters back in continuous mode.
The bass is very fast and tuneful, deep but not heavy. It puts to SHAME the normal bass you can get from a 7 inch driver in ported box a'la Proac Response 2,5. What a waste of time - the endless story about cloning those...
Female singers are as real and sexy as it gets. All of them sound gorgeous, Holly, Anna, Patricia, Diana, Ella, Marlena, you name them.
Drums and congas - you can write an essay about different types of drum skins.
Cymbals - the best I EVER HEARD no question. Finally the truth lies bare: silk domes don't come even close.
Long term listenability: be prepared and take sandwiches and coffee to the listening session.
Do they show flaws upstream? You bet! You can hear everything all the way to the recording studio hardware. You can distinguish not only albums sounding different, but songs on one album, coming from different sessions you can easily hear. In mixed music you can hear mixes and edits on individual tunes, you can count the multi-tracks in the mix.