What's an innocent reader to do? Here we have one reviewer who's outraged by EMI's remastering of the Busch Quartet's legendary Beethoven while I find it eminently listenable. To my ears the upper third of the higher frequencies hasn't disappeared -- the latest technology doesn't surgically amputate the frequency range, to begin with -- and in place of the dry, boxy sound one associates with the Busch recordings, these have a bit of bloom. Pitch has been nicely stabilized as well. I guess you'll have to hear some samples and decide for yourself. I only want to say that as a veteran listener to historical recordings, these offered less ear fatigue and more pleasure than previous issues I've heard.
As for the readings themselves, the Gramophone's comments still ring true: "The Busch recorded nine of Beethoven's 16 string quartets for HMV and American Columbia during the 1930s and early 1940s. Though other eminent quartet groups recorded Beethoven during this period, none rivalled the Busch's reputation for getting to the heart of Beethoven's inspiration."
P.S. -- Given the variable sources, there is sometimes a bit of residual hiss (as in Op. 132), sometimes none (Op. 131), and violin tone can be a little squeaky or not, depending.