The mini games you get to play through streetpass are a delight and more evidence of the "Nintendo magic" I never gave it much thought at first but I've had the system since it released and I still play Find Mii and the Puzzle Swap. I have yet to even get the other games that have released which I heard are good.
I'm dieing for Nintendo to put out Find Mii 3 as a full blown rpg where I can navigate a world with my Mii along with a party of streepass guests. Heck, make my most frequent streetpasser be one of the enemies and have him build henchmen through my streetpass hits also. There is just so much that could be done from the simple Streetpass function its amazing.