The first version of the routine to set the letter terms only supported the Letter taxonomy being set for posts. It would be nice to be able to run it to set taxonomy terms for other post types and letter based taxonomies.

Note: For bigram's taxonomies s-letter and b-letter this was implemented using the bigram-second-letters.php batch routine. Any changes to the oik-a2z functions may need to be reflected in the bigram code.