I've been using WHS since when it first came out. I recently upgraded to WHS 2011 (2 weeks ago). I might be unique as I can't see having an additional server, so I run WHS 2011 as a guest in VirtualBox.
My Host machine (my HTPC with a Silverstone case fits right in with my audio Rack) is:
Windows 7 Ultimate 64-bit OS
quad-core I5 CPU
16GB RAM
3 1.5 TB drives (2 for WHS backup)
My Guest Machine is:
WHS 2011 (Windows 2008 R2 64-bit server OS)
1 CPU
4 GB RAM
My main reason for have WHS 2011 is to support my Wife's bookkeeping business and I need an easy way to back (and potentially restore) her primary desktop, primary laptop, secondary laptop and her kitchen laptop for cooking / tracking / internet surfing. As she is making real money, i can justify the server / backup external drives and get to tinker with this nice product.
i'm in the middle of adding hardware to the Host machine. Adding a 2nd Ethernet Card so that the Guest VM (WHS 2011) will have it's own instead of bridging the Host Adapter. Seems to be much slower than my WHS2003 was on the same host machine. I probably just need to tweak my VM parameters to improve the performance.
Anyway, I here now.