KVM works. I'm happy with it. But then I build servers with 6 guests or less for small businesses. There are comparisons. They say KVM doesn't scale as well. They say in some areas xen shines, and in some areas kvm shines. But the comparisons are all from last year before red hat released 5.4. RHEL 5.5, which includes many improvements will be out shortly. Think I'll stick with it...