Ubuntu 12.04 LTS has some great improvements over the older version.  Even through it is no longer working with Active Directory LDAP authentication due to the bug in the libnss-ldap that causing sudo no longer work with start_tls; however,  it does connect to Active Directory now (not LDAP) and acts as one of the Windows PC computer with Windows ACL (I do missed NFS mounts and using UNIX UID/GID as user account’s attributes tho).

Here is how to connect your Ubuntu system to Active Directory with likewise-open package:

• Go to ubuntu Software Center and search for likewise.
• Install like-wise Desktop utility for joining Active Directory domains (likewise-open-gui)
• After installed, run Active Directory membership app
• Enter computer name and your Active Directory Domain name
• Now it asks for an account that has the admin rights to join the domain.  This is same as MS-Windows process
• This is it.  Reboot the PC and now you can login with your domain username and password.