Who doesn't use QXs and what are your reasons?
I am thinking of going double broods next year on my prolific colonies and ditching the QX.
Double and triple Commercial broods, without queen excluders. Been running that way since the 1980's when we saw a German beekeeper running such a system.
Reasons? Complements a multi-brood box setup, works best with single-depth boxes (but Commercial deeps are dangerously heavy when full of honey, 80lb and more measured in ours). One super of honey effectively contains all but the most cramped of queens in the brood space below.
Generally beekeepers in this country give far too little brood space, e.g. the mention above of moving to a single 14x12 to "give space"... which to me is laughably cramped, since I run my colonies on twice or three times that comb area. I know 14x12 is seen as the holy grail by many here...
I agree with Chris that finding the queen can be tricky with 33 frames of brood nest, but there are ways and means and clues to be had. Swarm control was in fact easier because of the multi-broods used hand-in-hand with no queen excluders; our crown boards are split boards so we have all the equipment necessary for an artificial swarm.
Queen excluders are used as a tool, where we need to partition colonies, e.g. when queen raising over a queenright colony.
BTW, framed queen excluders are worth the price/effort premium of the unframed floppy plastic ones. Bee space shouldn't be ignored