This is the most cluttered my screen looks. When I have my PvP hotbar open and I'm on my SMN. This is because both my pet hotbar and my PvP hotbar are set at 100% instead of being smaller, which I honestly
should do, but have yet to do so.
http://oi59.tinypic.com/15oz391.jpg
This is how it looks on my WHM. I do toggle the PvP hotbar on and off, so it's only open when I need it. (Ignore my neighbor, he saw me log on and we started chatting, lol)
http://oi62.tinypic.com/20ffgx.jpg
Hotbars 1-3: Job specific skills
Hotbar 4: Party Finder, Achievements, Challenge Log, Companion menu, PvP Profile, Gold Saucer menu, Emotes, teleport, Eternity Ring, 90 second /dance macro (the most important thing), Chocobo, Gysahl Greens.
Hotbar 5: Mark 1-4, Ignore 1&2, Circle, Cross, Triangle (aka Dunce Cap for the person who keeps derping during raid), Waymarkers, Sprint, Limit Break
^ These are all things I use the most frequently, so I have them in an easy location.
Hotbar 6: Job specific PvP skills, some of my classes have PvP gearsets, so those are located on this hotbar. (This hotbar gets toggled on/off frequently, which is why it's way off in the middle of nowhere)
Hotbar 7: DoW/DoM classes
Hotbar 8: DRG who didn't fit on the DoW/DoM hotbar, Mount menu, Mount Roulette, Parade Chocobo (Flying mount), blank space for Storm Warhorse (soon), Square, Bind 1-3 (these are used specifically for PvP, mostly marking enemy team healers, so I have them on a side hotbar), and cheap leveling food.
Hotbar 9: DoL/DoH classes and Minion menu.
Hotbar 10: Minion Roulette, Ready Check, Dig, Armory Chest (easier to put stuff in my retainer/change their gear), Friend List, Player Search (I honestly don't use this one too much, but I keep forgetting where to find Player Search, so I just slapped it somewhere easier to find), Key Items (I think I originally had my Aether Compass here), Timers, HUD Layout (easier to turn off/on my PvP hotbar), User Macros (I don't use this one too much either and I know where Macros are in the menu, but this is just for laziness).
My hotbars aren't exactly overflowing, as I do like to keep a space between a group of skills/buttons, just so I don't accidentally click the wrong thing. But as they are already, imo, they're really full and really cluttered.