The Windows beta team is pleased to announce the availability of Windows Vista and Longhorn Server build 5270. This release is the December Customer Technology Preview (CTP). This build is not beta quality but is offered as a preview or our progress towards Beta 2. It will allow you to confirm bugs that have been fixed and begin testing features that have been added since build 5231.
I wonder which servers would trust beta software, besides Microsoft, to actually be reliable? At any rate, check out the post over at AnandTech.