Zend is sponsoring an ongoing monthly two-day Bug Hunt, and it starts today. And ge this--if you solve a lot of bugs, you get a Zend Framework t-shirt! And four times a year (each quarter), they will "evaluate overall contributions, including documentation, bug fixes, and newly contributed components, and award a developer with their choice of a Zend Studio license or Zend Framework Certification voucher." You can't beat that!
To participate, you have to sign a CLA, and you can download the form here: http://framework.zend.com/cla
As far as the issue tracker, what you'll be looking for is if the bug: * is simply the reporter misunderstanding or misusing code * is a request for a new feature * is a reproducible issue
Good tracking and good luck!