If you grew up several decades ago, then you would know the impact that vritualisation has played in both the server as well as the desktop space. It has allowed companies to reduce the total number of physical servers within the network while also allowing for extra capabilities such as high availability, redundancy, clustering and so on. It has also allowed private users to experiment with a multitude of different operating systems and applications without having to possess a expensive, high-end hardware in your home network.
Of late, I've been working on a project that requires the evaluation of current software based Unified Threat Management (UTM) devices. Obviously, I've tried using the usual suspects in terms of virtualisation such as VMWare, Xen, VirtualBox, Hyper-V, Proxmox, and VirtualPC, in both Type 1 and Type 2 hypervisor format.
However, I've found the most versatile for my needs has been, 'VMWare Server'. It can sit as an application on top of an existing Operating System, it can run other 'Hypervisors' within itself (such as XenServer and ESX/i), virtual hardware is reasonably easy to add/remove/configure, and there are reasonable logs and diagnostic messages for when and if a problem arises.
That does not mean that it is not without its 'quirks' though. Due to the way 'virtual networks' work you'll need to set read/write permissions on relevant /dev/vmnet? device files in order to achieve promiscuous mode automatically (this can also be achieved by setting them up manually using the 'promisc' option with the 'ifconfig' command and while 'iptraf' does provide the option the various /dev/vnet? device files do not seem to show up as options).
Switching to a singular technology can also lead to unusual consequences during 'changing times'.
I personally experienced a strange issue of sorts with VMWare whereupon switching between the various NIC modes (host/NAT/custom/bridge) would not take effect when using a particular VM appliance but did using others. The only way to get around it was by re-creating the VM.
Note, that in many cases performance and functionality of guest Operating Systems can be increased through add-ons such as VMWare Tools and third-party tools. Also, there may be a significant performance overhead/hit depending on your existing setup.
Not surprisingly, hardware technology has made significant strides towards commoditisation in consumer class hardware. In most cases, modern CPU's will have such capabilities built into their existing architecture. I used to use upgraded Dell Optiplex GX280/GX520 desktops because they were smaller, consumed less power, and were quite simply quieter. If you don't have specific, 'Whitebox Virtualisation Hardware' though there are options available should you wish to customise ESX/i or provide enhanced driver support.