I would have to disagree with that.  I speak very
few words of japanese, however I can pick up a lot 
more info watching a "raw" program sans subtitles
than a professionally dubbed version.

Two good examples would be Nadesico and Cowboy
Bebop.  The whole series Nadesico is basically a 
parody of many anime series and the otaku sub-
-culture.  A lot of the dialogue is filled with an
underlying sarcasm, the whole show pokes fun at 
it's self.  The dialogue is extremely witty, and a 
lot of this never makes the jump to the dubbed
version.  The same applies with Bebop and what's
happened to Ed's character in the show.  A lot of
her jibberish rhymes in japanese, however 
translated to english it's still jibberish, but
it doesn't rhyme anymore (probably why most 
japanese rap tunes have a lot of english 
dialogue). The bottom line is that she's no where 
near as entertaining as she is when she's 
speaking in japanese (I shake head whenever I
accidently catch a C.N. episode). 

Just my opinion...
vegetassj