The regular research has had interesting results like showing a distinct pattern of cognitive traits and values associated with libertarian politics, but there's no reason one can't use it for investigating LWers in more detail; for example, going through the results, "we can see that many of us consider purity/respect to be far less morally significant than most", and we collectively seem to have Conscientiousness issues. (I also drew on it recently for a gay marriage comment.) If there were more data, it might be interesting to look at the results and see where LWers diverge the most from libertarians (the mainstream group we seem most psychologically similar to), but unfortunately for a lot of the tests, there's too little to bother with (LW n<10). Maybe more people could take it.
Big 5: http://www.yourmorals.org/bigfive_process.php
(You can see some of my results at http://www.gwern.net/Links#profile )
I suppose I'd be willing to say that those are "facets" of a single property if presented with evidence that they correlated really rightly with each other, but, no, I wouldn't a-priori consider, say, sensation seeking and intellectual open mindedness to be different facets of the same quality.
They might have superficial behavioral similarities. To use Openness as the example, both sensation seekers and the intellectually open minded might go on a roller coaster - one for the sheer thrill and the other out of curiosity as to how it feels- but I wouldn't predict those two qualities to be particularly more correlated than say, Extroversion and Openness.
Or, to use Agreeableness as the example, I wouldn't expect conformists to be kinder -, even if the two are superficially similar in that they are less likely to get into fights. Conformity and kindness aren't two facets of the same diamond, they're just two mostly separate variables which influence how likely you are to object to things.
My criticism is that the Big Five lumps together qualities that aren't even particularly similar into one variable.
(Although, I suppose it is fair to say I'd expect high inter-correlation between industriousness, dependability, and extrinsic motivatability, so I guess you can chalk those up as facets of a single thing)
The big five aren't a-priori categories. They are supposed to be factors that come out of principle component analysis.