Having been burned by upgrading software immediately after it’s released, I waited until yesterday to upgrade to Mac OS X Leopard 1.5.8. I am using a 2008 Macbook and was running Leopard 1.5.7, and the upgrade was flawless. After a long download of 1.5.8 upgrade, plus iTunes and several other upgrades, the upgrade installed and after about 20 minutes and several automatic reboots, my Macbook started up and all is good.