1. Sun's shared source license sucks and this is why ZFS isn't natively supported in Linux.
2. btrfs will soon have better features/performance/stability than ZFS, and a better architecture to boot: http://lwn.net/Articles/342892/
"Soon", maybe, but it will take a long time for it to be Generally Recognised As Reliable. (For all I argue against buying I to a brand just because, I do like ZFS more with Sun's name behind it)
1. Sun's shared source license sucks and this is why ZFS isn't natively supported in Linux. 2. btrfs will soon have better features/performance/stability than ZFS, and a better architecture to boot: http://lwn.net/Articles/342892/