Whichever management tool you use, Virtuozzo Containers is very fast to work with thanks to the way it implements its virtualisation. Because a "container" (ie a virtual machine) is simply a bunch of links, the creation of a new one takes only half a minute or so, as there's only 60MB or so of stuff to replicate. The creation process is a simple wizard, and in fact if you want to create a number of identical containers, you can simply tell it "Make me five of these" as part of the wizard walkthrough. The wizard has half a dozen steps, in which you pick the obvious things such as which template to use, where to get IP addresses from (you can define virtual pools of addresses, which are allocated by the setup process), what to call the containers, and what resource constraints to impose. New in version 4 are the ability to use virtual bridged networks (version 3.x only did routed networks; bridging allows you to do away with the need to have a separate IP subnet for your virtuals, and lets the containers use existing infrastructure services such as your corporate DHCP server). Also new to version 4 is the ability to provide resource guarantees, alongside the imposition of resource limits that was part of 3.x. Oh, and as with version 3.x, you can dynamically adjust the resource allocations of your virtuals and thus go with the ebb and flow of the loads on your various systems.
The system comes with some simple templates, but you'll probably want to grow your own to reflect the particular applications you want to use on your virtual servers. Template creation was one of the less wonderful bits of 3.x, but in 4.0 they've realised this and have provided some tools to make it a bit easier - not least a wizard that hand-holds you through the process. Since the additional stuff (such as office applications or whatnot) in a template is simply another bunch of links, each instance is again only a few megs instead of (in the case of many of today's applications) several gigabytes per virtual server.
Since organisations installing virtualisation probably have a bunch of physical servers to migrate from, Virtuozzo includes a migration tool. Under Windows, everything is WS2003-based - so if you migrate a Windows 2000 Server machine into a Virtuozzo container, it'll first upgrade it to WS2003. With Linux, although the base operating systems supported are CentOS, Fedora, RHEL and SuSE, the way Linux distributions works (i.e. a base kernel and library set on top of which the distributions plonk their preferred application sets) means that the guest operating systems that can be emulated extends into Debian, Red Hat 7/9 and Ubuntu. And for those with a yen for clustering, both Microsoft and Red Hat clustering services are supported, along with Microsoft Network Load Balancing.
To summarise, then, the way Virtuozzo Containers represents its containers is very clever indeed - not least because implementing virtual servers as links vastly reduces the time to create/reconfigure virtuals and the storage space required. Although I don't get particularly excited about the promises for the future "manage all your virtuals from one place" releases of PIM, it can't be denied that it's a cool bit of kit - it's DHTML-heavy and very reminiscent of a Windows application, even to the extent that you can right-click on stuff and get pop-up menus just like a desktop app.
Virtuozzo was very neat when I first looked at it, and it's now even neater.
The only thing that might put you off is that virtuals are platform-specific - that is, you can only run Linux virtuals on Linux hosts and Windows ones on Windows hosts. But we really don't think that's a huge problem, since the majority of virtualised installations have multiple physical servers anyway - which means you just have to think about what host OS to install on each physical server