I've never seen a full episode of the show, so I'm commenting out of ignorance here, but the conventional opinion seems to be that the show went out on top, just as the eponymous creator intended it to in declining a $110 million from NBC to produce a tenth season. It's difficult to say definitively based on viewer ratings whether the show had peaked in the fourth season and had been churning water for a few years with an impending dip in the near future or if it could have maintained the same quality for several more seasons. It's said by some that Larry David's departure at the end of the seventh season marked a change in the show for the worse, but that's not detectable here.
Whatever the case may be, if I were a fan, I doubt I would've been too happy about the desire to nobly call it quits at the zenith. A good portion of the ride down from that high point to the nadir some number of years in the future is still going to be thrilling, and I won't cherish my favorite episode in season six less because season fifteen sucks so much. As Ed succinctly put it:
People keep confusing "past its peak" with "bad". There are usually separate moments when a series begins its downhill slide, and when it actually becomes bad.I suppose if I was more SWPL and actually cared about how shows I enjoy influence my pop culture status, though, I guess I'd have to be grateful for Jerry's decision.