As listed in the changelog :
http://www.mailchimp.com/api/changelog.php
* mod: v1.2: make 200% sure we are picking up any bool-ish value for
"for_archive" in campaignContent()
* bug fix: v1.2, v1.1: required merge fields that are not passed to
listSubscribe() must always cause exceptions to be thrown
* change: v1.2, v1.1: support to accept XML-RPC datetime objects in
our various date fields