my input is irelevent and only to reiterate what they all said its all about your hardware capabilities when upgrading,,, the vidoe card is of special interest .... and needs to be configured correctly immediately on install or their will be all kinds of problems.
Compiz is super important to get working right,,,,it provides much more than it looks like at first and its all necessary and needs to be set up and will crash alot at first until it gets stable... I prevented metacity from running at all as the window manager this helped alot ....I now have the cube and all the effects working on 2 monitors :)
As far as features the unity launcher hud and new tray light dm and gnome 3
are the way to go personally i am just now finding ubuntu stable and usable with this dist
i had way more problems before...
might take a bit to get it all set but 100% worth it