Earlier this week Apple made available the iPhone OS 3.0 GM Seed (build 7A341). It's the best build to date. Compared to the previous build, E*Trade's Mobile Pro application now works without crashes. Apple have also implemented one of my feature requests - the ability to retain the order of application icons between restores. So this upgrade was the smoothest of them all.
In the iPhone’s Settings page, push notifications can be controlled globally as well as for individual apps: