I don't know why people keep saying this. It's just not true.
I have played with people who gear swap like it's a compulsion. I would have had to create a macro for just about every ability i use to have prevent my target from being canceled. It depends on the extent the people you are with use the technique, and I think a lot of the people pretending this isn't a big deal and just useless whining have been lucky enough not to party with people who use it like a compulsive habit.
It's just irritating. I already have a zillion macros. I really don't have the room or the head to use a zillion more.
I gear swap a ton myself, but only with gear that doesn't cause the blink effect. Why? Because i know how annoying it is I don't want to drive other players nuts. Be nice if everyone else would afford the same courtesy.
I would only swap gear during a fight that causes the "blink" effect for rare actions you don't use very often - otherwise the annoyance you will cause others will far outweight the benefits gained IMHO.
This is a real problem and Square should get around to doing something about it that doesn't involve having to make 50 extra macros so I can spend more time flipping through rows of macros than I do actually enjoying the game. Perhaps they should simply add this <stal> command or w/e into the coding of the game so that the command is automatically used with all targeted spells and ablities. I don't know enough about programming to know if that's a realistic solution or not, but it is one idea.
And then there is the spam issue also, flooding my battle log with this annoying yellow message telling me something i already know. That needs to be fixed also, and is just as irritating as the "blink" crap. Gear-swapping during battle has just become too big a part of FF 11's accepted game play for it to be as clunky as it is today. It's time it got some refinements.