Build Info:
java version "1.6.0-rc"
Java(TM) SE Runtime Environment (build 1.6.0-rc-b97)
Java HotSpot(TM) Client VM (build 1.6.0-rc-b97, mixed mode, sharing)

Vista Build info: 5520

This bug can be reproduced on the older Vista build 5472 as well.

The insets for the tooltip is wrong. The text in the tooltip touches the border of the tooltip on Window LookAndFeel.

There is a bug filed for the difference in the background color http://monaco.sfbay.sun.com/detail.jsf?cr=6425225, on b84 on Vista Build 5365. This problem was not there, you can refer the attached screen shot of this bug http://monaco.sfbay.sun.com/detail.jsf?cr=6425225.