Conclusions

Xen is a very powerful virtualization solution. In contrast to other options such as OpenVZ, it has the advantage of emulating a complete computer in a fashion similar to VMware. Xen is therefore capable of virtualizing guest operating systems other than Linux.

It is already possible to run NetBSD 4 as a Dom U on Linux or as a Dom 0 for Linux Dom U's without any major difficulties. The only issue is caused by NetBSD's lack of Physical Address Extension (PAE) support, which makes it more difficult to install Debian than it actually should be.

Considering the speed at which Xen and NetBSD developers are working to achieve a solution to this problem, you can expect rapid progress in the trend toward virtualizing different operating systems on the same hardware.