Microsoft published a document listing and comparing Windows Server 8 Hyper-V features against Windows Server 2008 R2 Hyper-V SP1.
The following tables compare selected features of Windows Server 2008 R2 Hyper-V and Windows Server "8" Beta Hyper-V.
The tables include comments about each version's performance, as well as a notation about how well each feature is supported.
"The information contained in this document relates to a pre-release product which may be substantially modified before it is commercially released. Microsoft makes no warranties, express or respect to the information presented here," Microsoft stated.
You can download the PDF of the doucment here, or online read the copy embedded below: