1. If you need to import user profiles from Active Directory – read this Support KB -How to import user profile information of enabled user accounts from Active Directory to SharePoint Portal Server 2003 or Office SharePoint Server 2007 – To import user profile information of only user accounts that are enabled, use the (&(objectCategory=person)(objectClass=user)( !(userAccountControl:1.2.840.1135220.127.116.113:=2))) LDAP search filter.
2. Users which are disabled will be added to the “Profiles missing from import” view after the import has run again. Here you can manually delete them, you can also wait for three full imports – see http://www.gilham.org/Blog/Lists/Posts/Post.aspx?ID=488 for more details.
3. There is an interesting tool which allows you to populate your SharePoint Server user profile database using basic XML files as source on Codeplex MOSS 2007 utility for import/export of user profiles. Also check out the codesample about how you can automatically create my sites as well as the information about using powershell to set up SharePoint user profiles