Ubuntu is a Linux distribution which you can find many different opinions out there. As I have been using the latest of Ubuntu, meaning 13.04, for a while I have found it to be usable and reasonably stable in daily usage. There has been only one major problem which I have so far encountered which related to Pulseaudio and my sound system giving me a constant “complaint” about dummy output/input which rendered my sound experience completely nonexistent.
So in case someone else is having problems with Ubuntu 13.04 showing only the “dummy output/input” device here are some tips that will hopefully get problems sorted out.
1. Upgrade your system: Doing upgrades might be a good choice in a bleeding edge distributions like Ubuntu because generally speaking upgrades tend fix errors.
2. If you are not a fan of Lightdm: Try for example Gdm which gives you a useful list of available sessions by default. Gdm will certainly come in handy if you decide to install, for example, Jwm instead of Unity environment.
If you remove both Lightdm and Gdm and try something else as your display manager you might experience the dummy output/input problem in sound again. This is because for some reason Ubuntu seems to break the connections between the display manager and Pulseaudio when something else than the two “modern” ones are being used (meaning Gdm or Lightdm).
3. Do not use startx: Getting rid of the display manager completely produces the same problems mentioned above.
There is of course always the option to get rid of Pulseuadio and start using Alsa instead. However I will not recommend the previously mentioned option in Ubuntu since it might lead to a disaster. If the above simple steps do not help you I advice you to seek more help from Ubuntu forums.
Before you post anything to the forums do make sure that the problem has not been asked or solved already. As friendly as Linux forums are it is more than save to say that everyone dislikes having asked about problems that do not exist anymore, or have been asked already, because it is a simple waste of energy and resources.