The working definitions of "Magic" and "Magick" follow:
n. [Old Persian magos: sorcerer, philosopher]: Creating changes in reality in in accordance to your will.
n. [Old Persian magos: sorcerer, philosopher; English variation by A. Crowley]: Designed to reclaim the word "magic" from the slight-of-hand charlatans who had appropriated it. At this point, it makes you appear to be unable to spell a five-letter word.
Honestly, "magick" is like shouting from the rafters that Pagans can't spell (pun not intended, but very good). I can't find it in my dictionary. In fact, "magic" itself, when used as a transitive verb, is correctly spelled "magicked" or "magicking", which indicates that we're making an even bigger mockery of ourselves by using a form of the word that doesn't exist.
Let's consider the idea that "magic" means "sleight of hand". Looking at the definition in The American Heritage College Dictionary, we see that the first two definitions deal with what Pagans would consider magic, and only the third definition deals with slight of hand. (Incidentally, "magick" isn't in the dictionary.)
If you ask a person on the street (try this sometimes, because the look you get is very amusing) what "magic" is, they're most likely going to tell you that it's Harry Potter, Witchcraft, or superstition. They're unlikely to think of stage magic first.
So, yeah, I suppose I do have a problem with the word "magick". Just a little one *grins* It looks Fluffy Bunny, silly, and just plain dumb. Crowley might have thought it best to use the "k", but Crowley also had a lot of other bad ideas.
People will disagree, of course. They've every right to. But I won't be changing my ways for them, so I don't care if they change their spelling for me. :)
But then, I always liked wishesofastar's response to my statement that there are two English spellings of Hekate: Hecate and Hekate.
". . . To distinguish the 'slight-of-hand' magic Hecate from the ritual magic Hekate."