99$? Where did you check it man!
The router is at most 50$ or so, i see its not very popular on the US/Europe, but its pretty common to find it here in South America and google reports a lot of AU results too.
Its not better than the Fon, it has half of the memory for a start which really sucks, i cant get a Fon here (altought im trying to ebay one soon or importing one with a friend, i've got yet to see what ill do about that) because the service its not here yet, like i care about the service! :P
But yeah, its not better than the Fon, by any means, Fon is Smaller, its proven to work, has more memory, and its what everyone uses, i "choose" the DIR300 because thats my current router, no other reason, sometimes you just gotta try to work with what you have :P.
So yeah, if you can choose, get the Fon, thats a no brainer, but if you dont and your router has an Atheros SoC, give it a try!