Have you ever installed a addon pack from Curse or Used Minion from WowInterface?
Well if you have I think you have to many addons installed. I am using a limited number of addons and even then I could use less but I like a certain look and wanted to keep that look. I use about 10-12 addons and use both curse and minion to keep the addons up to date and current with files and bugs.
As you can see I like a clean and well kept screen and everything has its own place. Even the quest I am on has a place to load.
List of Addons I use
AtlasLoot – shows possible Boss Drops
Bartender4 – Action Bar
Auctionator – Helps with selling in the Auction House
Deadly Boss Mods – Tells me whats happening
Gatherer – I use for mining and skinning.
Prat 3 – Better chat windows
Questmaster – Helps with quest
Recount -Show DPS of Party or Yourself
Sexymaps- Better map
KGPanels – Pure up to you, But It ads some extra art if wanted
Perl Unit Frames – Clean Unit Frames for targets and your unit frames.
As you can see I just use a few addons to change my screen setup and bars and unit frames and what works for me.