Yes, they really reduce friction. People who use a hard leather saddle often find they need no other cycling-specific clothing; the padded shorts, etc. all become dispensable. The key is a hard, smooth saddle that supports you where you need support, and gives no unnecessary padding.
+1
I have witnessed many a flame war in these forums over Brooks saddles... but I have to say this:
Riding a Brooks saddle may change your cycling habits forever.
Many people misunderstand the purpose of cycling shorts with chamois in them. The chamois isn't primarily for padding... it's there to reduce friction between your butt and the saddle. A properly maintained Brooks saddle's smooth surface almost eliminates that friction. I own many pairs of cycling shorts that only get used for long rides. For anything under 40 miles or so, I wear regular unpadded Nike or Under Armor compression shorts or regular khaki cargo shorts. Cycling specific apparel is optional.
Just so you know how biased I am... I own 10 bikes and 9 of them are equipped with Brooks saddles.