I finally have finished the process of migrating from Home server 2011 to 2012 essential, and I have to say it is excellent.  I have a set up with 5 pc clients running 8 pro (two media centres below plasmas, two home office PC's and a PC in the granny flat) and it is so far extremely robust as befits a server OS.

Mistakes I made along the way for others.

1. I thought a 60Gb SSD would be great for the boot drive of the server (to go along with the RAID 5 5 tTb Perc5/i array).  Essrntials will not install on a 60 Gb drive solo, and if you have another drive running at the same it will install but puts the boot sectors on the bigger drive!!  Could not find a way arounf this, as all the cloning programs I tried dont support a server OS. Problem solved with a 180 Gb SSD.

2.  Windows easy transfer does not seem to work, dont trust it.  It goes through the motions of taking the old computer account and updating the Active Directory user account but nothing is in the new account.  This was true for Win 7 to 8 and 8 to 8.

Cool things

1.  My files on my Raid array created by Home server 2011 were recognised by the 2012 install and available
2.  Server 2012 backup from administrative tools (NOT THE DASHBOARD VERSION) supports incremental network drive backup
3.  For an active directory noob, user accounts were a doddle
4.  My OSX Lion PC was easy to bind and seems to work well

I used this ebook, which helped a lot, money well spent.

http://www.wegotserved.com/2013/02/18/windows-server-2012-essentials-step-step-ready-roll/

Highly recommended.

Ivan