When it was announced, Android 4.0 Ice Cream Sandwich was supposed to solve the widespread issue of fragmentation, first by standardizing upgrades and then by eliminating confusing custom UIs. Unfortunately, even though Samsung's devices have yet to see an update, the company has already taken the source code and built their proprietary TouchWiz interface into Ice Cream Sandwich.
As you can see in the video, TouchWiz doesn't necessarily look bad by itself, and it does work just fine. Still, it covers up the awesome new interface of Ice Cream Sandwich, which was one of the release's major features. Now, instead of getting a completely refreshed (and much better UI) when they update, Samsung users will be greeted by the same bubbly and colorful icons Samsung has been using for years.
Of course, there was really no way for Google to prevent this. The open nature of Android means that no matter how much Google says they don't want custom UIs on Android, manufacturers can just get the source code and do what they want. All Google can do is threaten to deny official approval (which wouldn't be a good decision when dealing with the top manufacturer of Android devices), or just try to make a new UI that is so good that it doesn't need any skinning.
This is what they attempted to do with Ice Cream Sandwich, and in my opinion they succeeded. It is the best and most refined version of Android yet, and fit to be distributed as is across all Android devices. I understand Samsung's need to differentiate themselves from the crowd, but I just wish that they could find a way other than covering up Ice Cream Sandwich with their less than perfect software.