PC Magazine on the differences between how Apple and Microsoft release a new operating system version. It’s night vs. day.
Microsoft releases the public betas in order to get feedback and telemetry from testers to improve the product. Apple, on the other hand, will drop its new OS down from heaven (or, rather, Cupertino), without soliciting a word of feedback on in-development code from ordinary users.
Known major changes in OS X Leopard: 64-bit kernel, QuickTime X, Grand Central, support for Microsoft Exchange servers. Add to that my prediction of no support for PowerPC Macs, and a new user interface theme, ala iTunes.