“Many-to-many Dance-off!":http://blog.hasmanythrough.com/articles/2006/04/20/many-to-many-dance-off, good article which shows the differences between has_many :through and has_and_belongs_to_many.

Also from the same author: “Why aren’t join models proxy collections?":http://blog.hasmanythrough.com/articles/read/150

Funny how these articles show up at the time you need them. ;)