I would like to see some file system benchmarks on fuse-vs-native (there were some on ZFS, but also others could be interesting).
A really interesting new technology is Rump, which provides NetBSD drivers in userspace on many different OSes, including Linux. fs-utils provides utilities to handle the file systems the Rump userland kernel provides.
Binary packages of Rump and fs-utils for a variety of Linux distros can be found at:
Disclaimer: I did the OBS packaging so I might be biased.