Mistakes that are being made:
1) Thinking that touch is superior to mouse, that touch is the future. That's simply untrue, mouse is quicker and more productive.
2) Focusing on first-time users too much, forgetting experienced users. Example - animations - nice at first, but get annoying quickly.
3) Trying to unify the tablet and the desktop interface. The optimal interface for tablets and for desktops are different.
For me the ideal desktop environment would be:
- take the classical desktop concept
- do a design update (Gnome 2 or Win 7 aren't especially pretty, the design looks outdated)
- add some nice features without changing the whole concept, e.g. some tiling support, useful keyboard shortcuts etc.