I would say its a good card, but its still very situational. You never see it in tournaments, most people would much rather use the 6 stars to make a Goyo, or a Brionac dragon. Not to mention rather then discarding card for its effect, you can discard cards for Brionac and take out synchros or what ever you need. (I know you can say that you can do that with arcanite magician but don't forget that hand advantage is VERY important in this game, which is why most people go with Goyo you cant beat 2800 ATK and a chance to steal one of their monsters.) In casual play is where this card really shines, magician decks are pretty high tier when it comes to casual play, most people wont play lightsworn, x-sabers, or blackwings so the only think you really have to worry about is bottomless trap hole, smashing ground, and the likes. As for a casual tournament the only thing it has to worry about are Aliens. However alot of casual decks play field spells this is a problem for the Citadel, even if it has 10 counters on it. If they play another field spell it will get rid of the Citadel, you cant get past a card rule, so playing another field spell dose not destroy it, only send.
Oh wow that turned into a rant. o.o; I will stop there.
O.o was that even useful? (reminds me of a card of the day.)