Hey, funny you guys should mention Cosmos, as that's the first thing I compared Vitamin to. 
 
So far, I've preferred the sound of Cosmos over Vitamin every time.  Cosmos seems richer and smoother to my ears, while Vitamin is a little harsh-sounding (not the first time a Waves plugin has sounded harsh to me). 
 
Vitamin does give you flexible multiband control, and has multiband stereo widening, but as far as sound quality goes it hasn't impressed me yet.  Will continue to try it out on various things for a while, though.  I could be surprised.
 
Cheers,
Eddie
 
P.S.  Cosmos is a cool TV show.  :-)

Eddie TX
 
So far, I've preferred the sound of Cosmos over Vitamin every time.  Cosmos seems richer and smoother to my ears, while Vitamin is a little harsh-sounding (not the first time a Waves plugin has sounded harsh to me).

My my ... what delightful news!  It's always nice to hear that some plug-in that stimulates your GAS is actually second-rate compared to one you've already got on your DAW.  Score one for the pocket book.