There's an interesting article on the subject at the New York Times web site:
While it primarily discusses WDW and the Saratoga Springs, it does bring up some interesting points, both pro and con: WDC still screws things up, and still can do some things which may seem small, but can make an entire trip.
It also mentions MiceAge. Woo-hoo!
My opinion is that it is the standard of excellence that Disney has set for itself that is so hard for it to live up to--when you set your sights on perfection, anything less than that stands out. When something really goes bad (as described in that article), it goes really bad.
Of course, WDW in 15 years has gone from 3 parks and two hotels to 4 parks and a multitude of facilities, where DL has gone from 1 to 2 parks (OK, 1Ĺ if you insist), and 1 hotel to 3--so you can argue it's hard to maintain that standard while you expand (dilute?) the product.
At the same time, there still is magic. You can find it nearly anywhere on a Disney property if you look. Does one outweigh the other? Opinions? Experiences?