I don't know, but as someone who's been working with 7-mode since 2006, I love cluster mode.  Specifically, 8.3.  SVMs, migrating volumes hot between aggregates and ADP are the big drivers I've seen that move people to cDOT.  Cluster mode has basically done to storage what VMware did to servers - virtualise all the client-facing aspects so you never have downtime on your service ever again, and this makes everything flexible.  Unified Manager is almost actually a single pane of glass for HA monitoring, System Manager is worlds ahead of FilerView (well, I actually use it sometimes, which I can't say I ever did of FilerView), and the CLI is remarkably powerful.

Obviously it's not perfect (oh come back Performance Advisor, all is forgiven) but once you've got your head around it it's miles easier to maintain and manage than 7-mode systems ever were.