The newly ordered batch of Dell Vostro 1014 Laptops have a ALSA sound problem. When you plugin the headphone, sound plays both on headphone and internal speakers as well.
The solution seems either to upgrade ALSA which time consuming and painful. Or pass the correct model name by adding options snd-hda-intel model=dell-bios to /etc/modprobe.d/alsa-base.conf.
For now I settled for simple workaround (that is easy for blind users). Created two shortcut keys to enable and disable headphones with gnome keyboard shortcuts.
Name: Enable Headphones Command: amixer sset Master frontleft mute Name: Disable Headphones Command: amixer sset Master frontleft unmute
The downside of this workaround is that you hear only single channel sound on headphones. If you managed to fix this problem on Ubuntu Jaunty, leave a comment.