I'm with mattm about using a reflective sash. The vest is certainly attention grabbing with the ANSI-II rated amount of reflective material on it, but I'm not a fan of the vest. I find it to be annoying as it flaps around on the multiple fast downhills I have on my commute.

The regular 2" Nathan Super Sash is pretty good, but I'm taking it a step beyond: I'm ordering 2" SOLAS sew on and making a full SOLAS reflective kit: Sash, 2 ankle bands, and 2 arm/wrist bands.