Well, what are pros and cons?
If I understand it right, the packages in "Universe" area are not checked by Ubuntu stuff for compartibility. But there are some packages that I need to use from outside of what Ubuntu offer. For example, my MUA is Sylpheed which Ubuntu don't have. I got it from Debian's unstable tree by including Debian's link in sources.list. But if possible, I would like to keep exclusive to Ubuntu's links. I also know that currently, there are npo packages list like what Debian have for Ubuntu but it's in the works.
So, what's in "Universe" area of Ubuntu? I don't like to screw this box up with something I don't know. Educate me, please.
All packages not in the "universe" and "multiverse" repos are 'officially supported' but the Ubuntu team. I think that means that you can hire them to support you if you have problems with what they have in their official repos (this is how the company makes their money). The "universe" and "multiverse" repos are community-supported repos. "universe" is free software, "multiverse" is non-free/different licensing (ie, nvidia drivers/realplayer/et all).
I've been using Ubuntu since September on five different boxes, and the first thing I've done in every case is added Universe and Multiverse to my repos. Universe/Multiverse shouldn't be considered unstable...it's just as stable as the rest of Ubuntu, the company just provides the disclaimer "use at your own risk" to cover their ass. Any software worth having for your desktop system is in Universe, so I'd definitely recommend you enable it.