That I just learned while perusing some Longhorn clustering docs.
1) GPT cluster disks are now supported. This should mean no more 2TB limit.
2) The Supported Hardware list is gone - now anything that validates is officially supported.
3) Clustering of virtual servers is now officially supported, so no more hacking virtual disks to get them to show up in multiple virtual instances. Caveat: The Parallel-SCSI model is deprecated, so it looks like virtual iSCSI is the way to get this to work.
and my personal favorite, quoted straight from the Q&A session:
4) "In Windows Server 2003 the way disks were identified was by the Disk Signature. In Longhorn clustered disks are identified by multiple attributes, including the Disk Signature and the SCSI Inquiry data. If a disk can't be found by one attribute, it will attempted to be found in another way. If found the service will self heal and update it's records of the disk. So in Longhorn disks will self heal and should elimate support issues of disk signatures changing and disks not coming online."
Finally! No more deleting and re-adding cluster disks when cluster services loses them!
Longhorn clustering should be cool. Now I just have to find another cluster to manage.