So what is the concept of the fast forces?
You get the iconic characters of the set in a ready to play package with a map or maps. Fast Forces characters generally are made with very solid (read: good to play) dials so that those just buying Fast Forces have a good experience.
I've felt every Fast Forces pack has given me great value, even if I had the complete CUR/SR set. If you're playing with limited budget or figure collection, Fast Forces are probably your best value for solid characters and map variety.