You can run z/VM under the LPAR and host multiple Linux images under it, or host Linux directly on the LPAR and use KVM to split it into smaller VMs. The penalty for CPU oversubscription seems relatively small with the almost a gigabyte of L4 cache in every processor drawer.
I'm not buying one (sadly it's a bit over my impulse buy threshold), but I'd love to play with one.
But nah. I am not touching it, until IBM gets their ducks in a row.