I think your comments are more focused on lab and dev environments than business production, but allow me to offer some counter arguments and points.

VMware now supports a lot of “white box” categorized systems for ESX and ESXi. (http://vmetc.com/2008/06/06/vmware-to-certify-broader-range-of-one-two-and-four-socket-systems/) Use those if you prefer not to use the popular server manufacturers when calculating cost. The calculator itself may not be flexible enough to enter those reduced costs, but it’s very easy to recalculate the results manually afterwards.

In my experience, ESXi installs on a lot more servers and hardware combinations than either Hyper-V or Citrix XenServer – mainly because of the 32 bit architecture option. I’ve tried to piece together different hardware too for ESX/ ESXi, so I feel your pain, but Hyper-V and XenServer require 64 bit hardware – period. That’s was new hardware purchase for me and a lot of companies. Consider this a part of the TCO for the solution.

Hyper-V does not require, but almost makes it impossible to use without, Active Directory and domain membership. That’s extra windows licenses for AD infrastructure. Granted, it usually already exists, but Hyper-V needs it. You can build a stand alone Hyper-V server if you need one, but have fun setting up the permissions and remote administration access. Don’t forget you have to install, patch, configure, and maintain the Windows OS for Hyper-V too. ESX/ESXi has patches too, but MS means more in the real world. It is what it is. That’s part of the TCO too.

If you are recompiling a CentOS driver you are probably referring to Xen and not Citrix XenServer? If recompiling drivers is even possible with the Citrix flavor is even possible you are talking about a skillset that is not too common in most datacenters today, and having to go to this level of administration will be frowned upon with so many other virtualization options. Add this to the TCO again.

Finally, maybe it’s just me, but when I think about support, DR, BC, and everything that will get me out of bed at 3 am I’d rather have a server platform from Dell, HP, or IBM. Personally, I’ll virtualize my cheap servers and consolidate them on to a solid server platform and hardware components with a support agreement for repairs and replacement. Once again, down the road, real word TCO.

Don’t get me wrong. I am all for saving costs on licensing with open source and white box mentality, but solid virtual infrastructure lets me do that stuff in VMs where the virtual hardware is uniform and consistent. Ultimately that means lower TCO for those components.

There are a lot of inexpensive server hardware options you can buy that aren't supported by VMware ESXi in particular.

To run your Xen and Hyper-V servers, you can in many cases utilize existing equipment, you can piece to servers using cheap hardware, like IDE controllers,

Got a bunch of servers with 3ware or Adaptec controllers?
Depending on the specific controller, with VMware ESXi you may just be out of luck!

The hardware support of Hyper-V is phenomenal (as I understand, pretty much any controller that will have a Windows driver)

So is XenServer's; pretty much, if the RAID card is supported out of the box, you can use it with XenServer.

I have also in several cases been able to take the manufacturer's CentOS driver, and recompile it in a way that it would work with XenServer.

With ESXi I would be out of luck.

The cost of totally replacing infrastructure and having to pick the high-end brand-named servers to be safe is a cost unique to ESXi.

With XenServer, or Hyper-V, one may be able to choose less expensive equipment than VMware would require, and then VMware looks more expensive in infrastructure cost department as well…..

There are a lot of inexpensive server hardware options you can buy that aren't supported by VMware ESXi in particular.

To run your Xen and Hyper-V servers, you can in many cases utilize existing equipment, you can piece to servers using cheap hardware, like IDE controllers,

Got a bunch of servers with 3ware or Adaptec controllers?
Depending on the specific controller, with VMware ESXi you may just be out of luck!

The hardware support of Hyper-V is phenomenal (as I understand, pretty much any controller that will have a Windows driver)

So is XenServer's; pretty much, if the RAID card is supported out of the box, you can use it with XenServer.

I have also in several cases been able to take the manufacturer's CentOS driver, and recompile it in a way that it would work with XenServer.

With ESXi I would be out of luck.

The cost of totally replacing infrastructure and having to pick the high-end brand-named servers to be safe is a cost unique to ESXi.

With XenServer, or Hyper-V, one may be able to choose less expensive equipment than VMware would require, and then VMware looks more expensive in infrastructure cost department as well…..