Everything from the non-functioning/non-existent coffee makers, to the replacement of the hallway side pull down blinds with poorly sized/designed blue curtains. The replacement of the built-in door locks, with those cabinet draw locks, is another poorly thought thru maintenance change.
While I lament the loss of the original coffee makers, I do understand why they were removed. First, because the attendant had to frequently stop to make a new pot. Second, because many people were burned trying to pour the coffee out of the metal pot, when the train hit a bump. Only poor maintenance and/or a lack of a budget to repair the darn things can account for the non-functioning ones now installed.
As for the pull down blinds, while they were superior to the curtains both in terms on ease of use and room darkening, they were very costly to maintain and fix. Both the cost of parts and the labor to replace them when they started breaking, was the reason for the curtains being installed. They cost next to nothing to buy, maintenance is easy, and they are simple to replace when there is a problem.
The same applies to the door locks. Again they were very expensive to replace and maintain, and they were also confusing to many first time riders who'd panic when they couldn't open the door, even though they had unlocked it. The catch had this odd habit of jamming with the train's motion. One would often need to push the door fully closed in order to get the door to unlatch. If the door moved just slightly open, even though the catch was still holding, it would put too much tension on the mechanism and it would not release. Additionally the "lever" that one pushed had to be pushed just right, as it swung on a pivot point. If one pushed too much on the top IIRC, then the door would not open. One had to push harder at the lower end of the "lever", again IIRC (I might have it backwards as it's been a while since I've seen a working one).
I personally let more than a few people out of their room who couldn't figure out how to open the door because of the above issues, and I'm sure that most attendants had to do the same for their charges. So again to avoid those problems and reduce maintenance costs, the Viewliners have gradually had their door locks replaced as they rotate through the refurbishment programs. I think that there are probably still a few that haven't had the locks replaced, I had one last summer, but they are becoming rare. Note, these are the same style of locks that the Superliner's have had for years.
Could Amtrak perhaps have found some better answer to the shades and the locks? Possibly, although I'm not sure what they might have done. However it is clear that the built in shades and locks were a costly maintenance nightmare for Amtrak. So they choose the tried and true methods that have worked in the Superliner cars for years, when confronted by the much higher maintenance and replacement costs of the built in systems in the Viewliner cars.