I've been looking for a replacement for VMWare Server 1 for a while now. I'm having serious problem with time drifting in VMWare Server 1. I've previously tried VMWare Server 2 but it was really bad (for reasons I now have partially have forgotten). Oh, I remember that one problem was that not all of the virtual machines was compatible with VMWare Server 2. They just didn't start.
Some of my colleagues have tried Sun VirtualBox. I first though that this was a client-only virtual machine software. But after reading the user manual I have found a way to use it like VMWare Server. VirtualBox can be run on a server computer in a headless mode (read: only command line, no grapchics). For example:
> VBoxHeadless -s "Lennart test" -p 5000
This starts the already created virtual machine registered as "Lennart test" and listens for remote desktop connections on port 5000. Then I use my favorite remote desktop program to connect to the virtual machine (for example the build in Windows Remote Desktop Client).
I have not tried running graphics intense applications yet but my initial guess is that it will be a bit slower then the VMWare equalivance- VMWare Server Console. But I can be wrong...