What appealed to me about using Btrfs was that I could dynamically add more disks as I was inclined to upgrade, I could get data striping, snapshots, data deduplication (not implemented yet though), and since I was planning on running Linux, there was no practical solution for using ZFS. The fact that I couldn't pull the drive or that corruption might take things down doesn't concern me too much because if I wasn't using Btrfs I'd be using Ext4 and I wouldn't imagine it would be any better.
The documentation could probably use a little fleshing out, but in the little I've done (very little) setting things up, it was pretty straight-forward. As I said, I have two drives in my pool. When I installed Ubuntu, I only selected one for
I don't know about any automatic sharing, though, sorry. I'm sure it'd be pretty simple to set it up, but it might not be optimized for those cases.