kvm, for one. Not quite as featureful, and the UI is a command line (though there's the virt manager stuff that I haven't tried). But it's rock solid virtualization that never gives me problems.

I think people are misunderstanding this thread. This is a kernel developers thread, where Dave Jones is complaining that virtualbox is the source of too much random corruption and arbitrary crashes in the kernel, and he's submitting a patch that "taints" the module such the presence of virtualbox gets flagged in kernel panics (and thus automated bug reports, etc..).

It's unstable software, and that taint is important information that prevents people from wasting effort chasing non-bugs in other components. No one is flaming about it vs. vmware or whatever, or telling you what to use.