No it's not. It has its own set of problems. And bugs too! KVM has its pluses too, I agree, it's a VMM in kernel mode which apparently makes it faster, it is very non-intrusive to the rest of the kernel and hence got readily accepted upstream and so some might argue in that sense that it's better. But even though I have been hacking into KVM recently, for running a VM at home on my laptop/PC, I will always opt for VirtualBox for its simple ease of usage.