Scenario
I'm building a high-end workstation for a software developer. The plan is to install Hyper-V Server 2008 R2 SP1 on the internal disk, and create a Windows 7 Ent x64 VM in a VHD on a second disk. This second disk is an SSD in an externally accessible caddy.
Under normal use, the developer will boot Hyper-V, and then use remote control (initially the Hyper-V remote, but moving on to RDP) from the host to the locally running guest, and it should all work like a vanilla Windows 7 workstation. However, we also have a laptop with support for two harddrives, and I will replicate the setup there, so when going on a site visit, we plan for the developer to takes his SSD out of his workstation, put it in the laptop and Viola - there's his development environment.
Question
Can we run RemoteFX on this workstation so that both the server (RemoteFX in Hyper-V) and client (MSTSC) parts of RemoteFX are running on this "workstation"? If so, do I need two graphics adapters, and do they have to be identical? The objective is to provide accelerated video etc. for the Windows 7 VM under normal use.
I do not think Hyper-V Server has the capabilities you are looking for. For one thing, the UI is barebones, command prompt mainly, and lacks many tools you are used to having in more complex Windows versions (e.g. Windows Server). There is no Hyper-V Manager MMC snap-in, no mstsc.exe Remote Desktop Connection client to run, and so forth.
Also, I believe RemoteFX requires a Windows 7 client, so I do not think that route would work.
Even if you installed full-fledged Windows Server, which would give you more tools and a better UI, you would still not get the accelerated video you are looking for.
I am not sure of your overall goals or reasons for using Hyper-V Server, but you might consider something along the lines of VMware Workstation running on a Windows 7 client. This would support some forms of video acceleration in the VMs at the cost a little extra overhead beyond Hyper-V. Honestly though, on a high end workstation and/or SSD I doubt you would notice.
In all my reading, the requirement for RemoteFX is that the client use the Remote Desktop Connection Protocol 8.0 which there is an update for in Server 08' and Win7, http://support.microsoft.com/kb/2592687/en-us
I believe that this could work, but the only way to verify would be to try it. That being said, your hardware overhead for RemoteFX is much greater than some other solutions to this problem.
Server 2012 Standard offers a GUI option, and I just confirmed that it can connect to a Hyper-V guest machine with RemoteFX support locally via IP. That being said, you're going to get more performance running "bare metal" than running in Hyper-V. It also very much depends on what you're trying to do in the workstation.
An option that is new with Windows 8 is Windows To Go. It lets you run Windows 8 directly from a USB 3.0 flash drive. The performance is very satisfactory. And it supports the significant hardware changes that come with moving from machine to machine. If the only reason you're running Hyper-V is for hardware independence, then Windows To Go is what you want.