To a large extent, there are two issues.
One is a lot of people don't like change. Most of the changes in place are going to have very little impact for people who use their contracts as people on the DIS generally recommend - plan ahead, use your points at DVC resorts.
The second is expectations. Some people have fairly high expectations and when they aren't met, disappointment results. Not everyone gets a room with a great view in a great location. Some rooms show a little wear and tear. Sometimes check in is delayed. It isn't terribly realistic to get exactly the perfect room for a full week three months out. Sometimes people blow these things out of proportion - but honestly, sometimes Disney fails to meet minimal expectations - very late check ins, dirty rooms, mistakes made on the waitlist. Remember, however, that people will complain when something is wrong, but we get far fewer "perfect trip" posts - and the ones we do get don't tend to make interesting reading and don't have the front page life of someone who had a problem.
After six years of ownership, we still prefer the Deluxe resorts for quality and service - but we are quite content with the value we are getting from DVC - for what we spent on our points the ability to have a seperate room for the kids and a washer in the room and a regular, enforced Disney vacation makes up for what I believe is a little more wear and tear and a little less "magic." (Not everyone agrees with me, btw, plenty of people find no loss of magic and no loss of quality).