safari
good: look and feel of using a mac,
bad: designed for mac, not xp, unstable and slow. (is perfect on mac though)
firefox
good: loads of addons, customizable
bad: firefox 3 has horrible memory management, I've had it reach 1gb memory usage after an hour on youtube. If you choose firefox, try to find firefox 2
google chrome:
good: fast, easy to use
bad: new browser and unstable ( css not great, java applets mess up, same with flash sometimes)
Internet Explorer 8:
good: css problems of IE7 mostly fixed, very responsive
bad: has bad reputation from IE7, nowhere near as customizable as firefox.
I hope this helps