Please investigate and fix as needed the following issues related to upgrading to 2.0...
1. Handle "false entries" in civicrm_participant_payment table as noted in http://forum.civicrm.org/index.php/topic,2346.0.html#msg10167
2. Issues in custom field migration as noted here: http://forum.civicrm.org/index.php/topic,2401.0/topicseen.html
2.1 option_type field should only be REQUIRED for Radio, Checkbox and Select html types - need to investigate why this "required" rule is being thrown for upgrade yes/no, date or other types
2.2 I recreated the 2nd bug in this post. The link to "View / Edit Multiple Choice Options" should NOT be include at the bottom of the form UNLESS the html_type is Radio, Select or Checkbox. I added a Yes/No field and the link was displayed when I went back to Edit that field. This is definitely a bug.
3. Review this post (sql cleanup) and see if we can generically incorporate any of the cleanup snippets to help prevent errors during the upgrade: