ZFS continues to get so much attention, its really bewildering to me that Sun doesn't release it under a GPL compatible license. I mean, why bother open sourcing it if so many people won't bother using it because it will never make it into the mainline kernel?
Its already gotten a warm welcome from Mac OS X and FreeBSD, and I'd guess that more people would be willing to venture further into OpenSolaris if they had positive experiences with ZFS.
Meanwhile, btrfs is coming along, and will probably be done by the time the Sun executives figure out that they should release ZFS under the GPL. Oh well.