LH Beta 3 came out yesterday, and to go along with it, so did Network Access Protection (NAP) Beta 3. You can install the client on XP machines and other operating systems.
NAP is going to be a very nice feature for corporate networks and especially terminal servers. You can configure a terminal server to require connecting clients to send a health report on connect. If the client doesn't meet standards, they will be blocked and/or required to install updates/software.
Terminal Services Broker Service is taking the place of Terminal Server Session Directory and added a bit of load balancing logic into the mix.
There are a lot of cool things coming with Longhorn server.
The four areas I am most interested in are the terminal server enhancements, hypervisor, NAP, and the Core.
If you want to learn more about NAP, make sure to check out
this blog.