Others have listed likely problems, such as connection pooling issues as of Windows 2003.
I don't recall any other specific problems with 2K3, but there are Oracle 10g issues prior to 8.96_G1 which affect Financial Reports. Oracle 9i doesn't experience the problem.
If you have multiple enterprise and database servers (physical) its best to bake it in DEV/QA prior to rolling into PROD. When you do prod, in this fashion, it would be best to roll them in at the same time. Some have the opinion that one or the other should go first, but you almost always run into problems. Yes, you'll be able to eliminate one major factor as the root cause, but proper testing in QA would help you find these issues.
I've seen this done both ways, have done it both ways, and there will always be problems. Its all about mitigating risk.
