Removed all the apps that the iOS4 update re-installed on my 3G. Don’t care for that crap. Anyway, I had no need of them before and I had no need of them now. They will remain in iTunes should I ever need them.
Then I tried the hard (and soft) reset as recommended in this article via Macworld:
Bugs & Fixes: Seven iOS 4 troubleshooting tips
And those 2 little actions seem to have put the phone to rights. Downgrading the OS was gonna be a serious pain between the cheeks.