I just installed CNSD-200FM as well. Update went smooth except for a warning early in the upgrade process with a "can't read from card" error (don't remember the exact wording) but it had a retry option that worked the second time. Total time was about 50 minutes.
For the record, cards A and B are just variations of the same upgrade. A is for those who are still on v2.x firmware, and B is for anyone who upgraded to the CNSD-100FM 3.x firmware.
I went from 2.0 to 4.0 and the difference is dramatic. WAY faster and more responsive. Love it so far.
