I look at the IQ results for the survey every year. A selected handful of comments:

Karma vs. multiple IQ tests: positive correlation (.45) between self-report and Raven's for users with positive karma, negative correlation (-.11) between self-report and Raven's for users without positive karma.

SATs are very high: 96th percentile in the general population is lower quartile here. (First place I make the Harvey Mudd comparison.)

SAT self-report vs. IQ self-report: average SAT, depending on which one you look at and how you correct it, suggests that the average LWer is somewhere between 98th and 99.5th percentile. (IQ self-report average is above 99.5th percentile, and so I call the first "very high" and the second "extremely high.")

I've interacted with a handful of Nobel laureates, I'm familiar with the professors and students at two top 15 graduate physics programs, and I've interacted with a bunch of LWers. LW as whole seems roughly comparable to a undergraduate physics department, active LWers roughly comparable to a graduate physics department, and there are top LWers at the level of the Nobel laureates (but aging means the ~60 year old Nobel laureates are not a fair comparison to the ~30 year old top LWers, and this is selecting just the math genius types from the top LWers, not the most popular top LWers). Recall Marcello comparing Conway and Yudkowsky.