My power button is horribly broken so I can't get a screen shot...but...
1) Noticed that the pop-up iPod control says what "device" your sound is playing though... "Dock Connector" "Speaker" etc
To reproduce, go to iPod app, start a music song (not a video), then hit your Home Button once. Now back at the main screens, hit Home Button twice. While the song is playing move it into and out of the dock connector. The pop-up text will change. This is probably related to the "volume" control not appearing while plugged into the dock connector (as mentioned in the main post) since it's line out and the volume control doesn't do anything anyways when in "line-out" mode.
2) "Trick" the iPhone to play the music part of a music video while NOT in the iPod app screen (for example, place a music-only song in a playlist followed by a music video and while the music-only song is being played hit your Home Button and when the music video starts playing afterwards, only the music portion will play). Now go back into the iPod application. The music video will rewind about 2 seconds and start playing again while it resets the position in the music video's video output. Confused? Just try it. This did not occur previously, the music video would kinda skip a little and then play.