I'm loving the hell out of the new camera. iMovie is nice too. The video below is all shot from my i4 and edited in iMovie. I then uploaded to my computer and put it on YouTube from there (for the sake of quality).
The wind and lightweight of the device don't help the stability of the video either, but it's not bad at all. A stabilizer would just be an extra something in my pocket, and the whole point of one do-all device is the point of the iPhone 4 to me.