I think Joy Luck Cupertino peaked around the time we had the Great Dimsum Wars and a group of Chowhounds, led by Yimster, had a glorious feast. I remember thinking then that the quality was comparable to dimsum in HK.
In the past several months, we've been to Joy Luck Cupertino about two or three times, and have been increasingly disappointed each time. The wrappers have gotten thicker and coarser in the past year, the complexity of the seasonings has all but disappeared. The pan-fried rice rolls (chee cheong fan) were nearly tasteless. The once irresistible fried chicken wings were almost inedibly salty. And the noodle-wrapped Chinese doughnut was far inferior to the ones at HK Flower and Harbor Village. The steamed spareribs were still good, but $45 worth of assorted dimsum didn't yield anything that would inspire a trip from San Mateo.
Overall, it just seems that the cooks are not as careful as they used to be. And dimsum can excel only with care and attention to detail. Perhaps the expansion of Joy Luck to San Mateo (and oakland?) has caused the quality to suffer because it seems like they're churning out lots and lots of the standards and not paying as much attention to variety and finesse.