[this is a slightly edited version of what was originally a haloscan comment]
I have come to believe that it is crucial to realize that there are other factors in intelligence besides g and its subfactors (e.g. math/performance, visuospatial, verbal, short-term memory). This is important not only factually and scientifically, but politically as well; a less g/traditional IQ-based theory of intelligence and human biodiversity is probably both more accurate and more politically palatable than a heavily g-centered one. The main drawback is that such a theory is also unfortunately quite complicated and difficult to test.
Many apparently non-g factors are almost certainly correlated with g, but they are not the same thing. In terms of higher-visibility phenomena, this would mean factors like creativity, motivation/drive, consistency, effective planning. In terms of lower-visibility phenomena, this would mean factors such as (neocortical) left brain/right brain ability, efficiency, and interconnectedness, as well as the interaction of such entities with the paleomammalian/limbic/midbrain and reptilian/lower brain/brain stem.
The main problem, in my opinion, is that these factors other than g are much harder to measure, and virtually impossible to measure on a 3-hour test, much less a brain scan (given current technology). Of course there are self-report tests for personality, creativity, motivation, and the like, but self-report tests are not, in general, terribly reliable. Also, insightful multivariate data analysis and effective experimental design for such analysis is hard to come by because these tasks are extremely difficult for even an intelligent person (in both the g and non-g sense) to carry out. Thus the failure of “multiple intelligence” theories in spite of the fact that it is clear that there are multiple intelligences.
If you are still unconvinced, how else would one explain a 25-year old with a 150 IQ, but also with Asperger’s Syndrome/autism spectrum disorder, living on the streets while a 90-IQ illegal immigrant is living reasonably comfortably, and an intellectually uncurious and largely vacuous (outside of the classroom/lab/workplace) individual with only a 115 IQ is living large?(if you want a picture of the latter individual, think of Julia from (Orwell’s) 1984 transplanted to the real America ca. 2008, or the devoted Asian college student who seems to always be studying (high motivation/drive/tolerance for long, boring tasks) but has no intellectual interests and spends most of her/his free time with sleazy entertainment, sleeping around, smoking pot, drinking, and popping pills). Of course social factors such as biases against more autistic personalities may be partially at work, but most stereotypes and social biases have *some* basis in reality, even if they all too often facilitate cruelty and inefficiency. It is also important to remember that biological phenomena can lead to social phenomena (e.g. autistics, due to their biology, are repelled by (and repel) others, leading to a negative social reputation for autistics) just as environmental/social phenomena can lead to biological phenomena (e.g. autistics, due to their negative social reputation, increasingly have their biology wired for being hermits).
 and Being intelligent but uncurious seems to be substantially more common amongst Asians (and perhaps amongst high-IQ blacks and Hispanics/Amerinds as well) than whites, and more common amongst females than males. This is only my personal observation, and it may be an entirely sociocultural phenomenon even if it is real.
 Nothing against sleeping around, smoking pot, drinking, or popping pills, but these don’t tend to be the most intellectual activities in the world, in spite of common protestations to the contrary by horny drug users (such as, admittedly, myself) to the contrary. Also, I realize that immigrant (and particularly Asian) cultures are strongly biased against such hedonistic behaviors, but this bias tends to quickly fade amongst the children of immigrants, and even more so their grandchildren, as they become more modernized, Westernized, and Americanized.