It's not just the tone of the email or the new name that bugs people - it's the complete separation of their sites, pretending that the DVD-by-mail site can't communicate with the streaming-only site, etc. People are annoyed that their ratings/suggestions won't carry over to the new site, and that the streaming-site won't let them add a movie to their DVD-by-mail queue when they search for a title and find it's not a…
Actually, this is might be a great area for a third party to get involved. Inveni ( http://www.inveni.com/ ) already works with Netflix, IMDB, etc as a recommendation engine. It would be a pretty short step for them to start managing your Netflix/Qwickster queues.
Would be interesting to see if they have any plans to add that back, but otherwise, this type of solution sounds like it might not be possible.