Three comments:
1. Dump and restore is traumatic, but it's really the best way for large datasets. I think what it tells you more is: plan ahead! Know the limits of the filer you have so you won't have to do migration ahead of time, and when you do have to do it, know all the steps involved and have a good backoff plan. Also, backup and restore is much, much better than it used to be... I would not try this scheme with anything less than the latest software.
2. Your comment about the CDDI drivers is very true. I have also found the old Crescendo/Cisco cards to be lacking, and have had the best success with the NuBus CDDI cards.
3. Sounds like the bottom line for the mixed-shelf scheme is: "not yet." Still some bugs and lack of enough documentation.
Oh, and always go direct instead of through third-party vendors if you can, but I came to that conclusion a long time ago... it applies to almost all computer companies, not just Netapp.
Bruce
PS - How about the NTAP stock?