Is there a reason you need MacOS X as your server OS?

Plenty of other options out there which have more testing and have substantial history with ZFS. I'd seriously look into OpenIndiana or similar - I run this with much success on an HP Microserver, which has plenty of expansion possibilities with a small form factor, ECC RAM, etc.

If I was the developer, I'd see about giving away the low end version as a loss leader. As is, charging $20 = less people will test it = less stable.