Hi,
It seems that if I create a new (custom) post (using a front-end piklist form), the post is saved with all the meta-data that I specify in the form, but the same meta-data is not persisted in the initial revision that WP generates. Once I update the data from the admin UI, I see a diff between revision 1 and 2 where all the custom metadata fields are set. Eg:
Create new post, id 100. WP saves a revision, id 101. I update one of the fields (foo), save post. WP updates id 100, and creates a new revision, id 102. If I diff revision 101 and 102 in the admin UI, I would expect a diff for only the foo field, but I see that every meta field in the post goes from undefined/blank to the initial values that they had when first creating the post.