In their review of the high-end DALI PHANTOM S series, the German hi-fi magazine, Heimkino, finds the in-wall speaker range quite extraordinary.
Take-out from the review:
"Whoever is looking for perfect home cinema sound, does not get around large, space-filling speakers. Unless the choice is DALI’s Phantom S series. Although these in-wall speakers are also large and quite expensive, but combine excellent sound quality with an enormous living-room advantage: Built into walls they are almost invisible. In addition to this the DALI PHANTOM S Series reproduce an incomparable spatiality, silky-shining tones and gripping dynamics. Invisible high-end sound without compromise becomes reality by installing the PHANTOM S series - the reference in the In-Wall class!"
The full review is available here as an PDF (in German).