To use non-Apple headphone plug...
Granted, it's not ideal, but... I have an 1/8" to RCA cable I use in my car to play my ipod through the car stereo -- but with the iphone the 1/8" plug would not fit...
So, I took a pocket knife, and very carefully removed about 1/8" of of the molded plastic just above the metal plug, and that was enough that the plug easily fits into the iphone now, and it all works great.
Also, I will absolutely confirm (as the owner of 2 current ipods, and 2 previous models), that you cannot, once you sync one time, manually manage your music on the iPhone regardless of the iTunes settings.
Like some other people, before my phone was activated, I was able to drag an album on to it and it copied over. However, once the phone activated and sync'ed, it was no longer possible.
I am of the opinion this is a bug. But I am an optimist.
itripn