We have recently upgraded our ArcSDE 9.3 instance to ArcSDE 10. I was hoping to upgrade postgresql 8.3 to 8.4 at the same time. Although ArcSDE 10 supports 8.4, it turns out that the ArcSDE wizards do not. Everything must be done via the command line. I made the call to stick with 8.3 just to keep things easier. Am I missing out? Does anyone have any experiences with 8.3 vs 8.4 in ArcSDE, if so, what are your thoughts?
Although I can't help you on the feature comparison, I see that there are some scripts to make the upgrade process easier.