My thoughts exactly

"My only hope is they are not bought out by another big player, as they may stop development: my company has recently started spending cash with the intention of putting XenServer into a production environment!"

I'm just in the process of setting up a hosting platform for a new business and I was really excited about going with Xen. However when I did my research and found out they'd been bought out by Citrix, I feared the same thing and decided not to go with it.

My main concern is the free license. You have to renew it every year, and if it expires, you cannot reboot any virtual machines because they'll fail to come back on - so what if Citrix stop issuing free licenses, or get taken over and the new company stops issuing them? When I was trialling it, it took me 2 hours to find the registration page to get a free license; they don't make it obvious at all!

I'm now going with KVM on Ubuntu, which also sports live migration and is being backed by Redhat as their main virtualisation solution for enterprise contracts.

The best free hypervisor

It's certainly the best option for free virtualisation of Windows VMs, and the management tools are fair better than anything from the Open Source world. We've run our production web farm on XenServer for 2 years now, and had very few problems. I do worry Citrix will forget the standard users and focus on XenApp/XenDesktop. The pace of development and bug fixing in XenServer is definitely much slower than it was a year ago.