We already had a universal copy/paste in Linux: Mark with left mouse button, paste with middle button. This used to work for just about everything. However, lately browsers started to ignore this when I mark the URL and try to paste it elsewhere, for example. Instead I get the old clipboard. I have to use the left button multiple times - and it works. Falling back to Windows-style copy/paste, either with keys or pull-down menus with "copy" and later "paste" is, to me, a huge, inefficient step backwards and it's frustrating me every day.

Addon: For purely non-mouse work, think serial terminal, I for one want Emacs bindings. Though that's typically configurable for the shell anyway, so everyone can choose what they prefer.