With regards to some of the messages concerning SNG, there is a new beta of the FW available for download on http://www.ics.raleigh.ibm.com. If you have a spare RS/6000 kicking around, feel free to try it out (and send me comments, criticism and/or hate-mail).
Among some of the new features are Network Address Translation, a less-complicated interface for creating filtering rules, support under AIX 4.1 and 4.2 (note 4.2 has the new Sendmail 8.7 - as Dave Roberts has already mentioned), support for VPNs with compliance to RFCs 1825-1829, pager support, and inbound ftp proxying.
There was some talk of the integrity checking of FW files, and AIX does come with the Trusted Computing Base which keeps and compares checksums of all critical system files (using tcbck). The FW files can be added to the TCB. Although not in the current beta, the developers are working on MD5 hashing of FW system files.