I wanted to inform everyone that I have a production Terminal Server 2008 environment with legit "Per User" CALs. If you ever need a test subject, feel free to contact me. I am utilizing rdesktop 1.6 on my thin clients throughout the network. As noted by previous users, rdesktop 1.6 does not fully support Terminal Server 2008 functionality such as the "Session Broker" for load balancing.
I spoke with an Escalation Engineer from Microsoft this week about Terminal Server 2008 Licensing. He spoke about the size change of the Licensing Certificate Key from 512-bits to 2048-bits and the issues that was causing with other RDP clients. He also said that he has direct contact with the Terminal Server development team. Microsoft is currently fixing two bugs our organization discovered with Terminal Server 2008 Licensing in a 2003 domain. If there is a specific question you have I may be able to petition our Escalation Engineer to question the Development Team about it.