ZFS On Linux (ZOL) has come a long way in the past year or so. The developers have claimed it is production-ready with its recent v0.6.1 release. I've been running ZOL at home (still a pretty heavy workload, though) for a while now and I've had no problems. A lot of other people stand by ZOL as well.
That said, using ZOL as the root (or
/) partition is tricky. It is doable, although probably not worth your time. I believe that the Arch wiki has information about it.
The easiest path for you to take (in my option) would be to install Ubuntu on a separate boot drive (or mirror), install ZOL (from source or from the PPA), and simply
zpool import your existing ZFS pool.
Something to keep in mind: ZOL does not implement some of the most recent features of zpool (like encryption, among other things). It will likely warn you (and possibly block you) from mounting a pool that contains features that ZOL does support. Just in case, make a backup of the important data prior to trying to import it. I doubt anything bad will occur if it fails, but playing it safe is always good!