Just because you can, doesn't mean you should...
With Windows 2000 AD, you could not rename an Active Directory domain. Some feedback came to the product team that this feature would be useful in certain situations. So, in Windows Server 2003, you can now rename Active Directory domains.
But hold on! Exchange is tightly integrated with AD and this feature was not tested with all AD integrated products. Exchange 2000 does not support the renamed AD domains. In fact, even Exchange 2003 will not support this feature until SP1 of Exchange 2003 (See https://support.microsoft.com/default.aspx?scid=kb;EN-US;838623). Are there other products that this could impact? I would think there are (ISA Server, SMS, Cisco Call Manager, etc.), so be careful before doing this. I would take each product and verify that Microsoft (or the corresponding software company) has officially given support for the domain rename. Even with that, I would fully test the scenario in a lab.
That said, I would still debate why you would do this with an AD domain that is critical to a company. It is just a name right? Microsoft did test the feature, but there are so many dependencies on something like this, you'd have to imagine a possibility of issues appearing after this. It will most likely work, but why risk it? My opinion is that this feature is best suited for lab situations or that special one in a thousand cases where there is no other choice.