Adding to this, I've started using a macro that hides most of my UI but leaves the essential stuff up like chat. I also have it hide all my hotbars and then show a normally-hidden bar (set to minimum scale size) that only contains 1 button which executes the inverse macro that displays everything again. If anyone wants to try it, the relevant text commands are: /hud [element] [on/off] and /hotbar display [number] [on/off]. Here's the list of HUD element names from the play guide:

Target Bar (TargetBar,tbar), Focus Target Bar (FocusTarget,ftarget)
Party List (PartyList,plist), Enemy List (EnemyList,elist)
Parameter Bar (ParamBar,param), Minimap (Minimap,mmap)
Main Menu (MainMenu,mmenu), Server Info (ServerInfo,server)
Gil (Gil,gil), Inventory Grid (InventoryGrid,igrid)
Duty List (DutyList,dlist), Item Help (ItemHelp,ihelp)
Action Help (ActionHelp,ahelp), LimitGauge (LimitGauge,lgauge)
Experience Bar (ExpBar,ebar), Status Effects (StatusEffects,sfx)