For Windows and Linux, I also highly recommend the upgrade. I use it mainly under Linux, but my mother says it also made her old PC faster.
For Macs, I recommend using Apple's Safari or Camino. www.caminobrowser.com
I can't recommend Firefox for Mac due to expierience.
Internet Explorer? On the Mac: Trash Can. On the PC: Linux CD and reboot.
[This message has been edited by Theelectrikid (edited 10-29-2006).]