Yeah repost, I tried to look around the earlier thread but it's gone ;O
However, this is not an exploit. Spellsteal something, get summoned to a raid, go crazy, it's one of the oldest mage trick since TBC launch.
Is it worth it? Definitely it is, if you're skilled mage;
you know how to chaincast
you know how not to lose a single hot streak/missile barrage proc
you know how to time invisibility macro with quad core