Ryanjsoo posted a long and thorough review of the F9 over on Head-Fi. He also compared it to a number of other IEMs in the same market space, including the quad driver 1More. The sub-$100 space is starting to heat up.
Pros – Great build and ergonomic, Excellent treble extension, Detailed, Relatively balanced, Tuning tips
Cons – May still be too bright for some, Average isolation, Still not especially linear