Reiser4 is in a weird place after the conviction of Hans. I'm not sure I'd want to trust a production system on it. And I've been less than impressed with BtrFS on the test systems I've ran it on (though I'm aware there's others who swear by it - I'm only talking about my experiences).

ZFS is a fantastic file system, but I can't help wondering if part of the issue is the fact that the benchmarking was conducted on a virtual machine. ZFS is better suited for raw disks than virtual devices (again, just my anacdotal evidence. I've never ran benchmarks myself).