In the last six months, I did installed multiple HyperV clusters. One important issue which I faced in the initial days is outdated firmwares. This may not be specific to HyperV3, but this will become an issue once you enable HyperV3. I had issues while enabling HyperV role, sometimes while creating a cluster.
We are crossing 6+ months with Windows Server 2012. Most of the vendors has released the new firmwares for Windows Server 2012. I had issues where the specific driver was only available for Windows 2008 R2, where we cannot update it from a Windows 2012 OS. Installation will throw an error which says that incompatible OS.
Its always better to check each components and get the latest firmware and drivers prior to the HyperV configurations. If Windows 2012 is supported, you can try using bootable ISO images if possible.
Another important aspect of firmware update is due to the support for latest features like SR-IOV and ODX. The hardware may be having this feature but until the firmwares are updated to the latest one, we may not be able to use this.