As I said earlier this month [1], even knowing the secret to a magic trick doesn't diminish the awe in watching the skill and artistry in presenting the trick. Even Teller says as much [2] (link via Bunny). For example, although Penn & Teller are doing the classic Ball and Cups routine with clear plastic cups [3] unless you are paying very close attention, the baseball that pops up at the very end of the trick is still surprising.
[2] http://www.vanityfair.com/culture/2015/09/penn-and-teller-fool-us-revealing-tricks