While there aren't any dramatic feature differences between 2.8 and 3.0, here's a bit of useless information about what had to be done behind the scenes to get it working on a modern Mac:
• Compiled for Intel processors instead of PowerPC. Big-endian -> Little-endian issues galore.
• Carbon event timing is now on a short leash by the OS. A fair bit of work to get frame rates reasonably high again, including the use of GCD to get most filters to take advantage of multiple cores.
• Lots of old "type/creator" OSType stuff now uses file extensions.
• Rewrite sound input support and its display methods. Still not great, but it mostly works.
• Sandboxed and code signed for her pleasure. "Her" being Apple's App Store.