@ justinlee
Personally I don't feel it that much of a benefit for me, a) I monitor the >> Updates << topic in the general forum and b) I periodically visit the secunia site and run the OSI scan.
Whilst that is nowhere as comprehensive on the programs that are monitored as PSI, it is mainly dealing with the major ones, e.g. those more likely to be exploited.
I had PSI installed for a while, but I just didn't feel that keeping it up to date and running the scans was that much of a help given what I already do.