From my experience, most file processing patches have been without side effects ... whether it has been on the Attachment Service, MDS-CS, or BAS. In fact, I cannot remember one that had any side effects. No experience with this particular one, as we're running MR3 in production.
The impact of this particular bug appears to be narrow in focus in the BESX and BESD world, so legacy BES 4.1 administrators need not worry (unless RIM is pushing their "end of life" agenda for these platforms). BES 5.0 SP1 and SP2 have hotfixes available for the bug and BES 5.0 SP3 should upgrade to MR3, so the remediation paths are a little different (minimal to no impact versus possible impact depending on your installation).