Which OS should I pick for ZFS compatibility?

I'm in the process of building a new file server, and I want to use ZFS in a RAIDZ configuration with four 750 GB drives. The obvious choice is OpenSolaris, but I'm wondering if I should consider any other ZFS-compatible OSes, such as Nexenta OS or FreeBSD. I've heard that FreeBSD is not completely compatible, but that it's gotten better in FreeBSD 8.0. Nexenta looks interesting, since it's just the Solaris kernel with a modified Ubuntu userland. Does /prog/ have any advice?

2 again
if you value your data i wouldnt use it yet, that is my point

my dba is using it against everyone's better judgement but the DB is replicated and backed up