At the time of the ZFS presentation we were trying hard to move off NetApps- we had never-ending problems with WAFL (mainly caused by deleting 5TB from a nearly-full file system combined with snapshots). ZFS and Sun Fire were fairly early in their life cycles at that point so it wasn't "mature" enough for our enterprise use cases.

I still don't like the idea of combinging volume management with filesystem, but it's clear that it's worked well for many people over the past 15 years