Ok, here's our environment:

BES 4.1.1
Single BES server running local MSDE on Windows 2000
Exchange 5.5
320 users, about 40 users who appear to be still utilizing desktop synchronization (even though we told them how to enterprise activate).

We currently have a BES 4.1.2 Domino server up and running.

I know that this isn't a migration, because you can't move a user from Exchange BES to Notes, but I wanted to find out what the gotchas are on the client side.

For example, our plan is to wipe the BlackBerrys because I'm guessing that any Exchange emails on the Notes-connected device will not work as expected if the user is attempting to reply.

Also, the Desktop Manager - some people still use this, as mentioned. My thoughts were that we would send out a notice to the users stating that if you still wish to use the Desktop Manager, then you will need to run the setup and select the Notes option.

These are just a couple gotchas I have thought about - do you have any others?

What about the implications of the wireless backups? Exchange backups are pretty much useless, correct (once the move is made to Notes)?

Regards,
Rob

You'll not be able to reply to any previous Exchange mail entries on the recently Notes-connected devices. That's because there's no references on the server-side for those previous email.
It's better to do a security wipe of the device, that way the users will not have the option to select any "old" messages on the device to reply to. I'll assume that the Exchange server is still functional, then you can arrange to have some of the old messages (a select amount if you wish) "forwarded" to the new notes mail account.
For the DM, simply use the ADD/Remove app in the control panel and click the Change/Remove button. You'll then have the option to Modify, Repair or Remove the application. Simply select the Notes/Domino mail option.
As for gotchas - the address book (personal address book) is local to the mail client (located on client desktop). There'll be some additional configuration changes required to have wireless synchronization of the persoanl address book. I'll also assume that you did that already.

No experience of this so not much help with the questions, but welcome to the world of hassle free mail administration!

Well, I for one am happy we are moving to a system that was compiled in this century ;)