I love the Quadio box as a set, but the more I listen to it, the more frustrated I am with the mastering. That isn't to say it's a trainwreck by any means, but for me the set is more of a 'close but no cigar' proposition.
The whole thing seems to suffer from a kind of uniform 'smiley face' EQ (and it seems like some compression has been applied to the low end too, making it more "thumpy" than the original albums) that for me (as it seems others too) buries the vocals in particular.
Craig Anderson may be a skilled Blu-Ray author, but I think his relative lack of experience as a mastering engineer shows in this release - lead vocals and lead instruments seem buried under the sizzle of high hats, and the brass seems too brassy as a result of the treble boost. I know it's a cliche but I would have much preferred a more audiophile style mastering that slightly boosted the upper mids (ie maybe a wide 2dB boost centered around 5kHz) rather than the ski-ramp boost he's applied to the top end. Bob Vosgien's original mastering of CTA for the old Rhino quad DVD-V was just about perfect (and didn't exhibit any of the "buried vocals" problems that Anderson's Blu-Ray does), as was Bruce Botnick's quad mastering of the Doors Greatest Hits Blu-Ray - I wish the Chicago Quadio box had been more like either of these.
So I love this set for what it is, and the packaging is superb, but every time I listen to most of the albums from it (I'll agree, VII does sound very good) I despair when I think of all the work I'd have to put in to re-EQ it to make it match the tonality of the albums as they originally sounded.