A quick answer to your question is Yes. I did follow the 8.04 Virtual User How-To.
I carefully reviewed the two How-To's (7.10 and 8.04) and there were only minor differences. When it came to the quota notifications, they appeared to be identical. That is why I posted here in this forum.
To clarify, I am receiving emails daily with percentages reported. However, the maildirsize file that is placed in each user's mail folder is not being created or updated.
Therefore, the only accounts reported in the quota notification are the ones that were moved over from the 7.10 server to the 8.04. They don't appear to have been updated since the move. Any new accounts created after the move to 8.04 never have the maildirsize file created and as such, don't show up in the quota notification.