The newer alsa sound in Linux kernel has an issue with the headphone jack... Most distributions have issues with the newer Dell, Asus and other laptops which have the Intel 5 series or H55, P55 etc chipsets. These use the IDT codecs and work well on the normal laptop speakers.
I got a Dell 1749 recently and had issues with alsa configuration which resulted in no sound from the headphone. The same problem with other dell studio and XPS laptops that are using that chipset. Adding model=dell-m6 in the /etc/modprobe.d/sound (or /etc/modprobe.d/50-sound.conf in opensuse 11.2) will solve the issue.