It's a shame they haven't provided some benchmarks...
I can see using this for real-time applications alongside management stuff and for separating critical and possibly buggy kernel drivers to where they can't harm the rest of the system.
I don't think the benchmarks make much sense in this situation, unless you measure server utilization and performance guarantees (which is the dimension in which they differentiate themselves).
This is not supposed to fit into the same space as Xen or KVM; it's supposed to give the guest pretty much bare-metal control over the resources that you give it, with minimal interference from the host, so it can be used for real-time applications even if the host kernel is not real-time.
For those who don't know, a FreeBSD Jail is a virtualization on the OS level (rather than Hardware level as provided by VirtualBox et al). It's similar in concept to creating a chroot, but you're also locking down processes.
Jailhouse appears to be almost like an exokernel.
