Mods that are necessary? None really. Although there's a few things that most people do. The kick-stand mod and some protection for the back of the tank might help save its looks from nasty fall-overs or belt-buckles. And replacing the lower headlight bulb with a HID lamp is popular too (I must admit the stock low-beam brightness leaves something to be desired).
But nothing is really "necessary" to do to enjoy your Busa. Now... if you want to go nutz with the mods, that's another story. Just open your wallet and let the green-backs fly away!
For me, I like the stock look, but hey, each to their own. Your first order of business should just be, ride! Congrats on your new Busa!