CPAN was based on CTAN (used for Tex). Both are, IMHO, very high mental 
overhead archives to use effectively. So high overhead, I've never used 
them (or maybe it doesn't have to be that high to be over my head).

Off-Topic: For Tex, I let  Gerben Wierda pick what he thinks I need 
from CTAN and use his i-Installer app (http://www.rna.nl/tex.html), 
which is wonderful.

Back on Topic: I think RAA is excellent, much improved recently, and I 
understand it will be improved on a regular basis. I also like 
raa-install, because it handles dependencies so well (when they are 
declared by the developer, I think).