I subscribed from the first season through 2014, but abandoned it after that, because:
1) earlier seasons sort of followed a mission of presenting scores that either hadn't been recorded (or hadn't been recorded well), or that most living theatre-goers had had little-to-no chance of hearing done live. As they drifted further and further from that paradigm, my interest waned;
2) as the years went on, Encores began amplifying/miking the orchestra more and more, resulting in a sound that didn't match the original orchestrators' intentions (writing, as they did, for acoustic orchestras). Most people, I know don't care a rat's ass about this sort of thing, but a few of us do, and when a harp is a loud as a brass section, things just feel wrong;
3) Casting seems, to me, to have become increasingly sketchy, with performers of - let's say dubious skill often being used (when, I would guess, the better talent initially considered proved to be unavailable).
And if course, the price of subscriptions rose rather quickly to almost-Broadway ticket prices. Eventually, it seemed to me that I wasn't getting what I wanted. However, I doubt that my seats went unsold.