I've tested Astroidica and Sea Assault on the 3.1 version of iPhone OS. Both appear to work fine. There were no crashes on my iPhone 3G and there appears to be no major issues.
In some situations the audio seems much better in Sea Assault. In the iPhone OS 3.0, the audio thread for OpenAL might get starved -- especially if your doing heavy graphics. This was noticeable in the helicopter droning. It appears 3.1 resolves improves the issue. By starving an audio thread, I imply you might get some snap crackle pop in the output. This is good news. The clips in question always played well on my mac. So, I did not think it was a encoding/decoding issue. I'll have to do more checks but the initial impression is things are better. Should be less of a problem on the iPod Second Gen Touch and IPhone 3S because they have more hardware performance.
Everything appears to be functioning within the iTunes 9 application. Looks polished.
Looks like the latest update for Sea Assault was approved. Should be hitting the store in 24 hours.
Lots of things going on today.