I gotta go with suspension and chassis setup. I had my rear Öhlins rebuilt and at the same time serviced the front and got new Öhlinsoil in there together with springs and the diffrence is HUGE! Then dropped the front slightly and raised the rear and suddenly the bike was quick, nimble and extremly steady in the corners.
You could just set the suspension up (providing its working well enough), the stock stuff is good enough on the street, you just need to make sure it works as intended depending on when it was looked at/serviced last time and dial everything in. Spending a few bucks on a reputable servicecenter and getting there help to set everything up will go a long way towards giving you the right basic tool to start going fast on. But its entirly possible to do it yourself but depending on what you weigh a re-spring might be in order.
After that..
-Change gearing - 14/40 will give you free performance for low costs
-Lighter rims - I have Marchesini Magnesiums on mine and that was a HUGE diffrence!
-Better brakes - Just better pads will increase performance ALOT. I like EBC HH myself, but they are abit extreme for "street only" use.
-Exhaust - Not much in powergain, but the sound will have you smiling alot more.
-Camtiming and Fueling/Powercommander/chip - Gain midrange and driveability without much in the way of cost. Here is a report on camtiming and fueling gains. A buddy of mines bike, he says its silky smooth in delivery now.
http://www.hypertrick.net/reports/748Bip.asp or Bikeboy Brad Blacks report on camtiming a 748
http://www.bikeboy.org/748strada.html
So yeah.. Get the suspension fixed and setup first. That is the most crucial point to get right on any bike
//amullo