I have a benriner in addition to a French mandoline. The beni is quite sharp and does most of the things the bigger mandoline does. In addition, if you have to replace the beni, you won't feel too bad since it costs a fraction of the other!
I've got both, and I never, ever take out the big ol' Bron. Benriner all the way!
If you're near a Japanese or Chinese store, you can get one for about $25. Or you can order from here -- also $25. This company also used to sell replacement blades. (I found out about them from someone here on ChefTalk! :D )
"Notorious stickler" -- The New York Times, January 4, 2004