Sun had great engineers, Solaris is/was trash, but the ideas they came from it are brilliant. Oracle just bought them, they've brought nothing to the table since their purchase. Thankfully FreeBSD isn't ideologically prevented from incorporating ZFS and other good ideas from Solaris the way Linux is. Just because Oracle pissed in Sun's pool doesn't mean that the ideas are suddenly crap. Or do you refuse to use Libre Office because Open Office exists even though its now a part of the Apache foundation? Choose your ideological wars better, open source doesn't care who came up with the idea, just how its licensed and Sun did a good enough job giving back to the community that Oracle can't stop it.
That being said, ZFS is awesome, if you're not using it, try it. It's hungry for resources but having 4 drives drop out of an array at the same time due to a faulty backplane and ZFS not giving a shit was nice.