I'm one of those who've been saying the quality has been sinking, and I still think so. I've been a viewer since the first episode of "The Seinfeld Chronicles", so I've earned the right to be snooty. But to me, the shows now and last year just don't compare to the early days. They still have funny moments, but they're fewer and farther between. And the low points are definitely lower. The recent episode where Jerry races his old high school buddy was particulary bad, IMHO. Some of the lines there weren't far removed from a "Family Matters" episode.
In general, I think the quality of the writing has declined, and they're attempting to fill the gap with more broad humor and "wacky" situations.
Just my 3 or 4 cents.