This Tip/Trick is outdated now, with the advent of the 'Advanced Auto-Populate' tab/functionality. I've modified to the first post to indicate this, and will add a new Tip/Trick later this weekend.
PM doesn't currently do this (encrypt passwords) for passwords saved with advanced auto-complete,
While true for passwords saved according to this Tip/Trick, again, it is moot.
If you want to save a 'current' password, use the 'Advanced Auto-Populate' tab, and save it there in a 'password' field type - this WILL be encrypted. Be aware though that only fields of type 'password' are encrypted, OTHER field types are not. I think Eric agrees that this is a shortcoming, but once the RDF file itself is capable of being encrypted, it will render this shortcoming moot.