VMware Server is now free like free beer - and it should remain so after the beta. Great deal, because VMware is after all still the undisputed king among virtualizers - even under Linux. The open-source projects still have a lot to offer to get close to what VMware Server offers.
But if you want to try it out on your own host (which is quite easy due to the simple installation): make sure that the host does not have any other user accounts. Because VMware Server mercilessly uses all accounts that are set up on the system itself. Every user with whom you can log in - and that can indeed be a trivial mail user - can then create virtual machines and control public virtual machines (which are basically all created as root) and delete them.
The whole permission management is generally a bit of a hairy topic with VMware Server - it is decided based on the system permissions for the configuration file of the virtual machine. This is convenient - you just need the known tools - but also quite unintuitive during a first installation. And for example, I couldn't get the permission management for creating machines activated (for this, a special check file is created, whose permissions then say whether a user is allowed to create a new machine or not).
But once it's running smoothly (I had more trouble with X11 on the Mac - ssh -Y instead of ssh -X is the answer), it's a fine thing. Debian guests use minimal memory through the VMware tools, at least when they are not actively in use - and the management with the graphical console or the web interface is also quite nice. I think with a new machine this could really appeal to me - especially since you can then set up such a machine from the beginning with minimal users and push all services into the virtual machines.
However, I have already noticed that my simon is somewhat underpowered when it comes to virtualization. But a Hetzner DS 5000 or 7000 with extra storage could fit quite well there.