As part of a 'dev' machine setup, I run on my latop Win2008R2 x64 Hyper-V...why? to simply run x64 hosts.
Virtual PC, Virtual Server - will run on x64, but not host x64 O/Ss. So really the only option is Hyper-V in the MS land.

I present, demo + and draw all over my tablet screen on a regular basis as well as cut code in Server O/S.

The main problems I faced:
- was my display was dog slow, especially running VS2010, ppt or generally anything else that an average user might do.
- I remove the Hyper-V role off my machine and low and behold it's back to normal.

A student pointed me to a TechNet article - http://support.microsoft.com/kb/961661 in which the resolution is to install a VGA Display driver.
This is kinda not an option for me presenting etc.

Still I needed to run those x64 bit guests.
I was contemplating getting a monster laptop (the other day I was training with laptops that had 8GB of RAM, 6GB allocated to the VM!) or setting up various 'Demo RDP Connections' back into the office, so when I'm onsite and I need to demo then (somehow) I can get internet connectivity and RDP back to a server based VM - lot's of potential issues with this approach)

So the MS Story in this space at the moment is:
- 1) you want to run 32-bit hosts, VirtualPC or Virtual Server running on x64 or x86. Only x86 guests!
- 2) you want 64-bit guests -> Hyper-V (therefore you're looking at running Win2K8/R2). At work we have 15+ VMs running on Hyper-V machines really well, so no complaints there when running on Servers. It's just running it on my laptop where's it's not special.

Problem is - going fwd, the latest wave of Server Products, SharePoint 2010, Exchange 2010, CRM 5 etc....only run on x64

So onto to my unbelievable experience....

Last night I caught up with a couple of buddies Andrew Mee and Guy Riddle, where Guy mentioned all the pain he'd had in trying to get a x64 but guest up and running on his laptop. Here is his current solution:

Guy mentioned his setup:
1) Win7x64
2) VirtualBox - for VM emulation - WITH USB SUPPORT!!!! wow! In the land of BizTalk RFID, I had major issues with USB devices trying to be picked up inside the VM - 3rd party solutions etc. crazy.

He mentioned there were a few things to do around the disks etc...but he could run x64 guests on his Win7 machine AND the VMs FLEW!

So I thought there was a touch of the amber fluid talking and maybe he was indeed onto something. When I got home later that night I decided tonight was the night to refresh the laptop (fujitsu lifebook t4215/4GB/T7400) and Install Win7x64.

My potential issue with Virtual Box:
- I have a huge library of VHDs (parents, diffs etc) that for portability suites me down to the ground. I walk into a training room and can transfer my VHDs to the student machines and run them no hassles.
- If there's a VirtualBox specific format (VDI) then it yet another step in my export chain.

Alas - VirtualBox reads/writes VHDs automatically, unbelievable.

So I setup Win7x64 on my latop and got back to 9 sec bootup and shutdown times - gee that was refreshing after so long without.

I installed VirtualBox - it installed like a treat, and does 'snapshots' and has a great user interface. I didn't need to visit the cmd line once.

So now for the test - I was going to fire up my SP2010 Beta2 (Win2K8 R2 x64) VHDs, 40GB in size, differencing and Parent, straight from Hyper-V with Hyper-V extensions (in the past when I've done something like this, there's usually a blue screen invovled saying 'boot device not found')

Let's give it a crack I thought - all from the UI.
1) Within VirtualBox, I created a machine, added 2 CPUs, 1 NIC and 1400MB of RAM.
2) Attached the Child VHD from my SP2010.
3) I even had 3D graphic acceleration options for my VM, along with amd-v and 'nested tables' for some sort of faster memory access. Turn them all on I thought! We'll put it through its paces.

Started the machine......

1. upon first boot my hyper-v enabled VM booted straight up to the Login screen! Unbelievable I thought.
2. logged in and it found my NIC within 10 secs and was on the network within 20 secs (through NAT). If you've ever experienced a Hyper-V update where your Guests don't talk to the network anymore, until you put the new hyper-v additions on - you'll know the pain.
3. mouse/keyboard recognised.
4. I then thought - let me install the VirtualBox additions - can't hurt.
   
5. RDP support etc etc ...it's like shopping @ christmas - how good is this! yes I'll have that...and this...
   
   
   
   
   
   So back to Guy's immortal words - "it runs fast. Snappy, responsive etc"
   
   My SP2010B2 in 1.4GB RAM x64 VM runs fanstastic! - Fastest I've seen a VM run on my laptop for a long long time (unless it's WFW 3.11)
   

        It's just so refreshing to have a responsive VM running in reasonable memory. I found that if I allocated 2.5GB to a VM under hyper-v I wouldn't notice a marked improvement. It's not like it flew, and then I had to tweak it back to find that 'optimum sweet spot'

What an experience! What I'm seeing is that certainly for the desktop machine, VirtualBox can be a serious contender for x64 guests.

Thanks Guy for planting the seed!!!