We always make a pretty big deal of XenDesktop being an open desktop virtualization solution.  Particularly on the subject of hypervisor support, XenDesktop treats the 3 big vendors equally (Microsoft, VMware, plus our own XenServer).  But, just like in life, some are more equal than others!  Just using your existing production server virtualization infrastructure can unnecessarily drive up the cost and complexity of your XenDesktop deployment. The point is that Citrix has made a commitment to leverage XenServer and Citrix Essentials to the nth degree to make it the best platform for XenDesktop.  That is besides the obvious fact that Citrix Essentials for XenServer is built into XenDesktop (so that makes it free, as in free beer). See more on XenDesktop editions at: http://www.citrix.com/English/ps2/products/subfeature.asp?contentID=1685000 

So it is pretty important that XenDesktop users consider the benefits of Citrix Essentials 5.5 and XenServer 5.5 which are now available for download. XenDesktop 3 has been tested on XenServer 5.5 and is fully compatible and supported by Citrix.  And if you are already using XenServer 5, just click on the “check for updates” link.  A download is available on http://www.citrix.com/lang/English/lp/lp_1688615.asp

Here are some key benefits of XenServer which establishes it as the obvious choice for a XenDesktop deployment:

Best Bets for VDI Hypervisor Infrastructure
XenDesktop on VMW ESX 
XenDesktop on XenServer/ Essentials 5.5
Open Architecture Limited integration with storage vendors.
Full integration with any third party storage vendor.
Single Vendor Solution Multiple vendors
One “throat to choke” for virtual desktop troubleshooting and support.
Easy Management Complex support
Elegant design requiring minimal patching and updates.
Low Cost Expensive ESX licenses needed
XenServer included in XenDesktop license.

The StorageLink™ technology in Citrix Essentials ensures that XenServer is certified to work seamlessly with virtually every third-party storage infrastructure, array and backup system on the market today. The 5.5 release also adds the ability to fast clone and provision virtual machines, simplifying volume virtual desktop deployment. Watch a video covering these and other technologies on our blog: http://community.citrix.com/pages/viewpage.action?pageId=71237761

For more details, please refer to http://www.citrix.com/essentialsxenserver 

When using XenDesktop on XenServer, Citrix is there to support the entire solution.  In a mixed XenDesktop + VMware solution, troubleshooting and support will often be more costly and complex. 

XenServer is better integrated into XenDesktop than ESX, making for a better overall management experience for IT.  ESX introduces unneeded complexity to a desktop virtualization solution. XenServer will require less patching and maintenance due to a simpler and more elegant design.  For example, in the past 2 years since its release, XenServer 4.0 has required just 5 patches (link).  By comparison, in the 18 months since its release, VMware has issued 200+ patches (link) and updates for ESX 3.5.  Many VMware users were also bitten by the high-profile Update 2 bug last August (link). 

And, just to remind you once again, Citrix Essentials for XenServer is included in every XenDesktop license.  

XenServer 5
(as part of XenDesktop Enterprise Edition)
VMware vSphere 4.0 – 20 Servers
Capabilities: Multi-server management, resource pools, XenMotion, HA, workload balancing
Capabilities: Multi-server management, resource pools, vMotion, HA, DRS
20x Citrix XenServer Included vCenter Server + 3 Year Gold Support $7,670
20x Essentials for XenServer, Enterprise Included vCenter Server Heartbeat, 3 Yr Gold Support $15,347
1 Year support contract $1,500 vSphere Enterprise, 3 Yr Gold Support :
(40 processors)
Total 3-year cost $4,500 Total 3-year cost $199,625

Now that I have convinced you to give XenServer 5.5 a try, I should mention how easy it is to move your desktop VMs over.  XenServer’s Enhanced Conversion Tools make it a breeze to convert virtual machines created in the VMDK format (commonly used by VMware) into the VHD format. The new XenConvert tools also make it easy to seamlessly convert between any of the common open virtualization format packages, including OVF (open virtualization format), OVA (open virtual appliance) and XVA (XenServer virtual appliance). For more details, have a look at: http://community.citrix.com/blogs/citrite/richcr/2009/06/23/Citrix+XenConvert+2.0.1+Released%21 

The bottom line is that there is really no reason not to give XenServer a try for virtual desktops.  It has always been provided as part of XenDesktop and, now, the new features of XenServer 5.5 and Citrix Essentials 5.5 are compelling reasons to choose it for any virtual desktop deployment.