I'll try not to repeat what others have said, although I may just a little bit.
First of all, I didn't see the ending coming (aka. two black aces out of the box), that caught me off guard, so well done for that. However, if you just change the grip on the box, you can slide all the cards out in a second, instead of 15 seconds. Also, trick doesn't make any sense at all, so try to make it logical. Thirdly, if you could make two spectators signed cards appear instead of the jokers it would have a lot more power to it. Also, it takes ages for something magical to actually happen. You have to have a balance. The longer you wait for something magical to happen, the greater the magic moment needs to be (does that makes sense?).