I recently installed a new set of front and rear tires. This has really made a world of difference. Cornering has become easier, vibrations have reduced and the high speed shimmy is noticeably gone.
I put on Shinko 244s ( Rears 5.10-17 and Fronts 3.00-21 ) after reading up a few reviews. I wanted a tire with good road comfort, but also one that allows me to head out to Carnegie or Metcalf every once in a while. I was also considering the Kenda 761 and the Shinko 705 but they were out of stock (and also a little more expensive).
I also put a set of black gel grips ( Pro Grips 714 ) and that has significantly reduced the high speed vibrations.