Just put a set of A3's on my dad's GSA. I've ridden A2's for a long time in everything from pavement to sloppy mud.
Initial thoughts, just from a quick pavement ride, is the initial turn in feels the same. Nice and stable.
I'm going to be doing a longer ride tomorrow and will try to find some slick clay down here to test it on. The tread pattern is different but the grooves are deep enough that I think it'll almost be like a knobbie's edge. Obviously won't be a knobby, but I think it'll work just fine.