My migration steps were along these lines:
(and I just did this a within the last month)
1) Setup new hardware
2)Install msde on new hardware (tho, you may choose to use a sql server, we only support 30 or so blackberry users, so for us using msde was easier)
3) Upgrade domino to 6.5.4 on my 2.2 server - let it run a week or so to check for issues
4) Install/migrate domino 6.5.4 to new hardware using this document from Lotus http://www-1.ibm.com/support/docview...id=swg21087009
5) Migrate the BES 2.2 to new hardware (disconnected original 2.2 server/name change/network info change on new hardware), bring up server
Used document TAE-00117-001 from Blackberry (search on that # on their site to get document)
-- now my contact at RIM suggested once I did that migration, bring up the server and make sure it looked good, then take it down and upgrade right there. We choose to upgrade the BES after a 2 week period, just making sure all was good with new hardware, etc.
6) Install/upgrade new server to 4.0 (sp3/hotfix 4 i think)
--- we did have to contact RIM to get a new CAL to upgrade to 4.0, the SRP info stayed the same though
7) over the air, this is something we are still working with, as some of my users have handheld/desktop mgr software that needs updating. Also, with domino you will need a strategy to accomplish over the air updates (address book and journal), we are currently leaning towards making users roaming to accomplish this.
Your other options are replicating up to the server from the clients, and inotes, but this will require a sync on the users part.
We were also told from BB Support that users will still need to use the desktop mgr software in order for the server to see them cradled if they don't want to recieve mail on the handheld while at desk.
Of course I'm still in that 7 stage, so there may be other things that come up, we did see some strange stuff on users showing the sent from the client show up on the handheld, still a work in progress, so these are some of the things that I will still be working on.
That is basically where we are at on this same type of upgrade/migration, hope it helped, please let me know if you have any questions, maybe my recent experience can help me to answer them for you! Hope the above wasn't too cluttered up to make sense!