I am a sysadmin for more than 20 years now, and work for a lot of different customers (profit an non-profits) using a mix of windows and linux. I use Xenserver for virtualization for several years (started with 5.5) and i really like the product.
IMHO the best virtualization solution around.
I got caught by the 7.1 Citrix trick (don't mention 7.3) and I love the route to XCP-ng.
XEN is a beautiful product and should no be killed by Citrix,
and in the open it can blossom.