Thanks guys for the compliment.
As to trigger in system databases for patches/service packs, it's hard to tell. I think it also depends on each individual patch/SP. Some patches/SPs might modify a table structure. When that happens, this trigger might get lost. I guess it's always a good idea to check after each patch/SP is installed.
As to the deletion of a package, yes, a separate trigger has to be created to audit deletion of DTS packages.