The Preview is still out there and the first impressions were made.
Since R2 hits the TechNet i’m on my way to explore more and more stuff I really like.

• Tiered Storage Spaces
• incredible fast (Windows) updates
• dedup for CSVs
• shared virtual disks (makes it a lot easier to build Cluster in a Cluster Environments –> guest clustering)
• online VHDX resizing (Gen2 only)

But there are some Points missing.

A graphical view of hot spots on dedup’d File Servers or something to see what kind of data can dedup’d pretty well and what kind doesn’t.
Quick upgrade/migrations paths for existing Gen1 Hyper-V machines to Gen2.