Hmmmm, ok time to insert my newbie foot into the conv
First let me say that I'm coming to PVE from a different direction than most.
I actually had a been working at a company (out of work now guys, who's hiring?) where I was maintaining roughly 800 physical servers running initially Xen (3.0-3.2 hypervisors) that I was transitioning to KVM.
I went out on the web hunting for a solution to centrally manage a large number of servers/clusters of KVM machines. Let me say that PVE definitely has a great deal to offer above those who want to run a KVM only environment.
While it is true that their are several decent x based desktop apps for maintaining KVM machines, there is a lack for stable web interface based solutions. I found enomalism to be under documented and a pain to maintain, I didn't like the direction ubuntu's landscape software was going with commercialism, etc, etc, etc.
Proxmox VE does an amazing job of providing a simple, clean, working interface with a bare metal installer! Most importantly, it didn't try to lock me down to a single storage model like LVM.
So when I initially started to use PVE in the past week on my home environment I mainly looked to it in order to migrate existing KVM machines; my experience with OpenVZ was nil. However in seeing how much easier VZ would be to use in order to build small daemon hosts (DNS, RWHOIS, websites) I have to admit to liking the containers from an administrative standpoint. Hell, I had at one point in the field over 40 KVM VMs just running DNS forwarders.
However, ease of use aside, KVM appears to be the course of the future at the moment and I certainly understand the development teams need for the newest kernel, etc. What I would ask however, is why not try to use the libvirt API? Allow different Proxmox nodes to run different kernels/hypervisors (mixed in different combinations) and limit creation/migration depending on the selected destination node?
I know this is a much more involved direction, however it would mean the largest amount of hypervisor support and allow the PVE project to expand to a much wider audience.
Just my two cents, please excuse me if I've mistakenly opened past wounds/discussions.
--David