I replied to the thread via patch instead ;) Everyone has different ideas on what a filesystem should be, and my goal isn't to convince everyone that Btrfs fits their definition of ideal.
Ohad Rodeh's paper was really about snapshot reference counting. He did go into details of btree balancing but this was mostly about how top-down balancing is best suited to the snapshot reference counting problem.
We've definitely changed some of the fundamentals around snapshot reference counting too, and we've continued to discuss these with Dr Rodeh (he's really good to work with). His work was presented as a starting point for people interested in snapshotting.
There are also a lot of ideas from reiserfsv3 and xfs and ext in Btrfs. To me, filesystems are really just a collection of tradeoffs and optimizations for specific goals. We trade CPU for disk IO, or CPU and disk IO for features, and these tradeoffs change as we go.
When designing btrfs we took a big pile of known solutions for filesystem problems, crammed them together, and then fixed up the new problems that resulted. Somehow I missed the scientific magazine step that all the other filesystems have followed, but I'll do what I can to keep improving the FS.