The UI i use on my mage.
Addons
Elk Buffbars - A very clean way to display buffs with timer bars
Dominos - A full action bar replacement
Atlasloot Enhanced - A great addon for finding out what gear u want
Icehud - A very visual replacement to the blizzard player, target, and vehicle frames
Minimap Button Frame - An amazing clutter reducer that collects all the addon buttons around
your minimap and put em in a simple moveable bar
Sexymap - A very nice replacement to the normal minimap
MoveAnything - nice to move ui elements thats in the way
Grid +
Grid Mana Bars - An exeptional replacement to the blizzard raid frames.
Recount - Damage/Dps/Heal/Hps/Everything else tracker
Omen Threat Meter - Self explanitory
Rating Buster - Compares gear with your own and shows the + and - of stats you will get from switching gear
CBH Viewport - A very simplistic and effective viewport
Decursive - Makes decursing seem like childs play
Broker Portals - A simple clutter reduser for mages that puts all the portals in a minimap button
Mik Scrolling Battle Text - Very nice combat text
Simple Marker - A raid leader assist addon that makes marking easy.
Satrina Buff Frames - Buff frame made by Tankspot's own Satrina, I use this addon to display
my targets buffs and debuffs.