I'd been holding off upgrading to Snow Leopard because of compatibility concerns. I was particularly cautious about it working with Perian and Flip4Mac. So thanks for posting this!
I think that Quicktime X is more a hot new developer API for the moment really, Apple's handling of it for the user-end though is a bit confusing. I'm hoping that Quicktime X will evolve quickly to re-introduce all the missing functionality, and hopefully support for .mkv etc.