Here's something positive and interesting I have noticed running iOS4 on my iPhone 3G. I stream Internet radio through the Wunderradio App. In the past, when I receive a phone call the app dies and I must restart it to stream music again. Since upgrading to iOS4 somethign different happens. I have a Yada Bluetooth handsfree device in my car to receive phone calls on. I have been streaming music in Wunderradio and then received a call. After hanging up the call the Wunderradio app returns to continue streaming music without any intervention from me. Now how cool is that? Just like the iPod functionality.
I also love the folders. This is worth the upgrade all by itself. I do notice some delay when starting apps but I can live with that. And as much as I have been reading about issues with iOS4 on an iPhone 3g, I don't seem to be experiencing them. I'm still very happy with my iPhone and am waiting until my upgrade date with Fido to get the new iPhone 4, which should be next month sometime. YeeHaw!!