As a sample of one, I have been running Leopard since its release with maybe two crashes in the whole time. I use several mail apps, several browsers, Apple apps, Office 2004 and 2008, and Solitaire Til Dawn, and AOL radio, among others. I regard myself as I'm a heavy and advanced user. The apps crash occasionally, but the system has been rock solid. It's revealing that the posters that complain about system stability in one post, in another post mention all the non-Apple adapters that they use. Through the years I've found that hardware gizmos and "enhancement" software are often the culprits in system crashes. Which makes sense when you think about it. Jon