RIM put together a great page on comparing BES 4.1 SP6 with BES 5.0 for both Exchange and Domino.

For those of you that are contemplating the upgrade ... or will be contemplating the upgrade it is worth a read. Be sure to take note of all the features that require handheld OS 5.0; which we'll hopefully see before the end of the year.

Check it out: BlackBerry - Enterprise Server Compare - Microsoft Exchange - IBM Lotus Domino