I've heard two rumors regarding action bar skills:
Using action bars addons capable of creating more bars than the default UI provides causes skills to lag since the action bars aren't "real" action bars (i.e. they don't use the "Action Bar Functions" keybinds).
Using macros to denote modifier behavior causes abilities to be used slower than creating separate bindings (i.e.
/use [nomod]Fireball;Pyroblaston A instead of binding Fireball to A and Pyroblast to Shift + A ).
I am a user of the Macaroon addon. It is an action bar addon that allows an unlimited amount of bars, each of unlimited size. Every button in the action bar is a macro (if you drag a skill into a button, it will change the button to say
/cast skillName). As such, all of my bindings are on bars that are not part of the default interface, and all of the buttons are using macros (and they aren't even part of the default macro interface, either).
Is their truth to the rumors? Is my setup harming my gameplay?