Xen vs. Citrix Xenserver?

The news that Citrix is planning to give away their Xen server product has people talking. I think it's very interesting how this announcement was made:

The new free Citrix XenServer release will be available for download from the Citrix website and other download portals by the end of March 2009.

But.. the product page at Citrix says a free version IS available now..

Here's the interesting thing: Citrix Xenserver requires a 64 bit machine AND a Windows box to manage it. You can download the free open source Xen from The University of Cambridge and run it on 32 bit hardware and without a Windows client to manage it. So why should you care about Citrix Xenserver?

OK, Citrix probably has added stuff. Specifically, they've probably added hooks for their Citrix Essentials for XenServer, which is NOT a free product. If you need that, obviously you'd want the Citrix Xen rather than the open source version. They may also have made it easier for non-technical people to deploy - though I have to wonder why non-technical people would be dabbling in virtualization at all!

As a sub page specifically notes that "You can buy support", presumably that might be a reason to choose this over raw Xen.

Aside from the annoying requirement of a Windows management box, is there any other reason not to embrace this? I'd be worried about divergence and lock-in: will Citrix keep up with the Xen project or will they lag behind because of the need to keep their hooks in place? On the other hand, is it possible for Citrix Xen to leap ahead of the Xen project in features?

Assuming you don't need the "Essentials", would you ever consider a corporatized (I can't believe spell-check didn't flag THAT!) version of a product that is freely available as open source?