XFS: the filesystem of the future?

The other thing to consider about shrinking is that without a LOT of work, it will almost certainly give you a "best fit" into your new space, not an optimal layout. I've seen extN filesystems that have gone through a lot of shrink/grow/shrink/grow and the result is quite a mess, allocation wise. That's not really even a dig at ext4; if you are constantly rescrambling any filesystem like that, you're going to stray from any optimal allocations you may have had before you started...