Citrix has made their hypervisor based virtualisation product, XenServer, available for free. There has been a free "Express" version out for a while, but this was limited in the number of VMs it could support and came with a limited subset of functionality (similar to ESXi).
The new release makes most of the Advanced functionality available for free, including multi-server management and live migration between hosts. This competes with VMware very well, to the point that a virtualised Citrix (XenApp) solution I am working on will most probably run on the free XenServer and not on the pay-for ESX.
So why do I wonder whether XenServer has a future?
Citrix are looking to get customers hooked on XenServer with the aim of upselling a management suite called "Citrix Essentials for XenServer". The thing that concerns me is they also have a product called "Citrix Essentials for Hyper-V".
On the one hand this makes sense. By providing the same management tools for both XenServer and Hyper-V, Citrix are trying to make the underlying hypervisor a commodity item. The real advantage is in the management layer.
But development of XenServer is not free, and Citrix get no money directly from it. So why bother continuing development in the long term, when they can "superset" on top of Hyper-V, a hypervisor that Citrix don't have to spend any development funds on.
I hope I'm wrong, because XenServer looks interesting, but it wouldn't surprise me to see a future announcement where Citrix drop XenServer and adopt Hyper-V as their favoured hypervisor.