Compass issue fixed (it’s about time!)
It looks as if iOS 4.2 aggravated the occasional problem with the compass getting stuck on North. That helped me track it down. It apparently wasn’t an iOS bug that I originally thought, but came as a result of something that was really badly documented in the way the magnetometer was being handled. And 4.2 made it more sensitive to that issue. My 3GS on 4.1 works fine, but my iPhone 4 on 4.2.1 was hit and miss when it came to aiming. But anyway, I posted the fix to the Appstore yesterday so hopefully it will be out by the end of the week.