The AUR is wonderful. Ubuntu's support for PPAs comes in at a close second, though less from a tech standpoint and more because of Ubuntu's massive community. Both provide a middle ground, inbetween the ideal of the package manager (which almost always works) and the frustration of trying to build the software from source. With the AUR, someone else has resolved most of the kinks for me already, and that's time saved that I can really appreciate.