The Master of Illusion downloads allow you to perform magic on your DSi to amuse yourself and friends, so if something like that amuses you, these might be worth checking out. Funny Face is the most impressive of the tricks, but is also the most complicated to learn and perform effectively, which might make it too complex for anyone who isn't actually an aspiring magician. Vanishing Card might be worth showing to others, but it comes with all of the downloads, and unless you're willing to learn the complexities of Funny Face, one of the other tricks might suit your needs.
All of these tricks come from the retail version of Master of Illusion, mind you, so if you own that, you don't need these, and if you're a fan of magic tricks, you might be better served buying that instead. Funny Face is really a very good trick, to be fair, but it's a hard trick to really master, which makes it more of a product for someone who actually is interested in magic than someone who just wants to play around with some tricks.