I have played quite a few of the different synthetic reeds: Hahn, Hartmann, Bari, Legere and Fibracell.
The Fibracell reeds are on the bright side, but played quite well for me. They are more reed-like than the Hahn, Bari or Hartmann, but a bit buzzy. I think they miss out on the flexibility and tonal richness compared to the very best cane reeds but are a reasonable substitute with a fair number of advantages (play from cold, last a long time, few duds).
On SOTW, people have commented that the Fibracell reeds aren't as consistent as they used to be, but I have only played a few and can't comment on this.
Last week I bought a Legere Signature reed for tenor sax and that is easily the most reed-like in sound of any of the synthetics I have played. The softest reed that I could buy was a 3.0 but that feels a little too hard for me, so I have sent it back to exchange for a 2.5 (Legere offer a very good returns policy).
Hope that helps
Rhys