When merging two constituent records - both with Membership records - allow for the Membership information to be merged rather than copied. This way Membership history is still preserved on the record and you don't end up with lapsed Memberships or dropped Memberships on a record that never should have been there. The only way to avoid this situation now is to manually update the Membership record after the merge is completed.
Expensive tool and worth it - if it's fairly easy to use.
Also, membership transactions are locked once a new transaction is entered. There's NO WAY to unlock a membership transaction, to make changes. As a result, changing date joined, or moving a payment from one transaction to another, is very difficult. These actions, as well as merging memberships, requires deleting all transactions, and reentering them manually.
Blackbaud - we need a membership unlock tool, like the batch unpost plugin.