I never really understood why people feel the need to keep the UI mostly the same. It may not be as good at the first release, but why do people object to them breaking everything at first? What, was everything perfect already?
Because they didn't leave any option to "break everything". If the new stuff was mature when released it might be a different story.
Some people actually have work to do however and don't appreciate being forced from a 2.0 to a 0.5alpha without option. Unless you wanted to stay on an unsupported dist for years as I did with Natty (until recently).
Despite my complaints, experimentation is fine in my book... The best way of handling this would be to ship Gnome2 and 3/Unity side-by-side and let the user choose, but 2 was dumped immediately for something broken, unknown, and undocumented. There's no way to stay current without "busting" your desktop.
Because users are accustomed to the Previous Version. They have various specific ways of doing things. Your new UI breaks it, so now the user has to spend time readjusting their habits. It gets even worse if there is no simple, obvious way to re-establish the old workflow.
