I just wanted to pop in to say this has been a great thread to follow. Thanks for starting it!
Can someone say what the various password strength fields (ps, pbe, and pgrng) are used for? When creating new items, what would I lose by leaving those fields out?
Those overview fields are used to display the relative password strength value.
ps is the value for manually entered passwords and is used to display the relative strength value.
pbe describes the bits of entropy used for generating the password
pgrng denotes that pbe should be used for password strength display
by omitting ps or pbe/pgrng all your passwords will likely show up as weak in the 1Password interface.