Here's my experience with BES v4.1.3 Hotfix 2:
1) Filters - Create a filter for a user, on the server, which restricts which emails are allowed redirection to handheld. Once the filter is applied to the handheld it automatically changes the condition from "No" to "Yes". The "Yes" needs to be manually changed to "No" on the handheld in order for the filter work correctly. RIM T-Support: Known issue that will be addressed in the next Hotfix.
2) Address Book Synchronization - Assign an address book for a user, on the server. Let the address book synchronize to the handheld.
Disable address book synchronization. Clear the address book entries on the handheld through DTM.
Wait 4 hours (specific for GroupWise System Synchronization/Update)
Assign the user to a new GroupWise address book, on the server, and re-enable synchronization. Either two things will happen: a) You will not get an address book synched/pushed down to your handheld b) You will receive an address book but it will be the OLD address book that you were synchronized to previously. RIM T-Support: Known issue that involves the Synchronization Service not picking up the new information. Currently have a call with 2nd level escalation to investigate this issue.
... and that's my experiences so far with v4.1.3 Hotfix 2!