The "Directory Utility" has been removed from the "Utilities" folder. You can still access Directory Utility by going to System Preferences>Accounts>Login Options At the bottom, it reads "Network Account Server:" with a "Join" button. If you click "Join", you get the option to open Directory Utility!
I've joined my MacBook Pro to my Windows Domain at work and it is a disaster. The computer joins just fine and has a connection to the Active Directory server. I log out, log in as a user on the network, create my Mobile Account. Everything is fine - until I restart. After restart the computer cannot establish a connection to the Active Directory Server, which makes my mobile account take 5+ minutes to log in and when it finally does log in, it strips the mobile account of admin privileges. I'm not on wireless, I'm hard wired into the network.
Any suggestions on how to fix that? This is feeling eerily similar to 10.5.0 through 10.5.5 in terms of reliability for being able to actually be a part of a Windows Domain on a mobile computer. I was hoping Apple wouldn't slip backwards again...