Interesting comments, I don't agree with the "no advantage comments" but I'm only about 6 months into my FG/SS and 3 years into cycling. My Wabi feels very different to me in FG mode. It's hard to describe so I'm going to say it feels more connected to the road. In SS mode it's not much different than my geared roadie.

I put mine in SS when I go to the race track (motorsports) and use it for paddock transportation. I always flip it back to FG when done. The difference is big enough to get me to flip back to FG. If it matters, I've left both brakes on it regardless of SS or FG.