This topic relates to some stuff I've recently discovered (as in the past day or two) about myself, and I also have a newfound appreciation for my parents, because they didn't let me see any results from standardized tests growing up, and it's only because I 'found' a folder in my mom's desk that had all the results...so now I know. I look forward to talking to her about it!! ;-)
I grew up in IL, where they did OLSAT (Otis Lennon) intelligence tests starting in 3rd grade, and each yr up through 7th grade. In 3rd grade I was above average, but nothing special. By 5th grade I had gotten into the 97th percentile, and I continued to improve. The OLSAT measures SAI, which is equivalent to IQ. My 7th grade Non-verbal IQ was 125, and verbal IQ was 139, for composite of 132.
The GRE up through 9/2001 is considered an intelligence test (from 9/2001 and later, though, it is not, because they re-vamped the test structure). I took it in 2/2001, and scored a 2090 total (verbal + quantitative + analytical). Lowest composite GRE score Mensa would accept is 1875 (and lowest IQ they accept is 132), so since my GRE is rather higher than 1875, I assume my IQ is higher than 132 now. --> Or, WAS.
**However**.

It is now 2007, and I have had 6 yrs worth of jobs that under-utilize me, and frankly I don't have to 'think' very much on the job. I haven't exercised ANY math skills for years, and I KNOW I've gotten dumber. I know it. It's kind of scary! Makes me almost want to break out all of my college notebooks and re-learn everything I used to know, because I'm becoming really...mathematically...dumb. Tied to this, I have to spend more time figuring out something, that would have been an almost instantaneous knowledge 5-10 years ago. My brain cells and neural pathways have totally become under-used, so I need to do something before they completely atrophy.

It's like many pathways of my brain have gone into semi-hibernation.
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To answer a few of your questions - I do think IQ measures ones aptitude to learn and excel in academic settings, and thrive in those settings. And I think it correlates to how easy it is for one to learn, and how quickly one picks concepts/theories/etc up.
However, you know what they say...often the more book-smart one is, the less common sense he might have. Less social intelligence, less emotional intelligence, etc. And, this would be why there are equally valid intelligence theories out there. I mean, I think emotional intelligence is vastly important in the 'real world' - and the real world is about interacting with people - and those with higher IQ may have more issues with this aspect of life.
Also, I think anxiety and depression are rather common for those with higher IQ's. I know both are beneath the surface in me, and my brother apparently has a higher IQ than I, and he has severe social anxiety, and was diagnosed with chronic depression several yrs ago, but appears to be much more functional, and happy, now.