Beta 3 was just signed off and will be posted very soon to connect.microsoft.com. There is so much coolness in IIS 7 in Beta 3 that's hard to know where to start. We've had several customers beating up this build pretty hard, including Microsoft.com. This is a good build for the web server platform (can't speak about the rest of it cause I don't know, but from the looks of things, it's all good).
Of course, you've heard all about the modular pipeline. Right? what! Snap out of it! This is a big deal.
Shared configuration: You can now configure multiple IIS 7 servers to share a single application host config file. Whohoo! No more metabase replication.
Remote Administration: This is coolness in action. Use https from within IIS manager to connect to another IIS manager. Since it's https, it's firewall friendly and not special ports need to be open. You authenticate to the remote IIS manager using Windows users, or you can define users in the IIS manger that are stored in Administration.config (encrypted credentials of course)
Disable Anon user: So if you disable the anon user in IIS7, anon access is still allowed, but you don't use the built in IUSR account. All anon access occurs as the process identity. If you give each process a unique identity, you also give it a uniqu anon users when this is enabled. Add sandoxing and shared config, and you have a nice package for web farms with secure pools.