Just finished a P2V Windows Small Business Server 2011 P2V.
What made it a little more difficult was the server that SBS was running on was going to be the hypervizor too. So I had to P2V to one of the customers desktop computers in VMware Workstation format then install ESXi 5.1 U1 one the server then move it back onto the server.
How I did it was I turned off every service I could think of. It was only about 300 GB of data it took I think it was about 15 hours to the Desktop Computer and then I think about 8 hours to the ESXi Server from the desktop. Had a small issue with email sending but that was it once I fixed that everything worked perfectly.
Issue with the email sending:
In the end, it was restarting the MS Exchange Mail Submission service ONLY that allowed mail to be delivered again!! Reference From http://community.spiceworks.com/topic/140865-convert-exchnage-2007-physical-to-vm-esxi
This is a risky thing to do please proceed at your own risk. I was able to pull the original disks so if it failed I could go back to the physical server. I had the customer buy two new disks (we need the extra space anyway) that is what I used for the ESXi.