I've been using PGP Desktop for many years both on PC and Mac platforms. I've not had much trouble on the PC. However, the Mac PGP Desktop has always been problematic. I've experienced major stability issues with almost every update or OS upgrade. If you are on Tiger and planning an upgrade to Leopard, be careful. Some of your most valuable data might become unaccessible. If you are planning to deploy PGP Desktop for the first time, consider your alternatives like open source. Apple's own AES-secured disk images are not bad at all. But it's not that simple as there's mail security. In any case, please check out my blog at http://pgpsucks.wordpress.com for tips and stories on PGP Desktop.