Re: custom user fields
http://tikiwiki.org/tiki-index.php?page=UserPreferencesAdmin&highlight=customfield
can help
It is very simple. The fields are text and viewed by everybody
The user tracker is a more sophisticated approach. different field type, visibility by field. A user can fill it at any time but not at registration time in 1.9
You need 1.10 to have a full integration of tracker and registration