Frankly, not much - but it's not like I think they are doing bad things it just seems like it's yet another philosophical forum.
I was active from 2007~2010 when it was just transitioning from the Hanson/Yudkowski combined blog with a robust comments section to the beginnings of what you see now. I'm sure some of my comments are still floating around there somewhere.
I think in the early days it was a pretty good place to bounce ideas off of each other about philosophical ideas/concepts WRT AGI, and probably still has that to some degree. It just became too cultish around Yudkowski for my tastes and ended up being very navel gazing around Bayesian probability and "rationalism" as religion. That's not to denigrate Bayesians or rationalism at all because those are great things.
In the end the community is more interested in talking than they are doing and SIAI is somewhat of an offshoot of that ethos with roots in the original Future of Humanity core group, and continues that legacy.
Don't get me wrong, there are a lot of really smart great people contributing interesting things there about rationality and optimization. I just moved away from their religion of rationality that boils down to these super hardcore utilitarian calculations which end up kind of defeating the populist goals of spreading rationalism.