Psychometricians generally regard IQ tests as having high statistical reliability.[7][45] A high reliability implies that – although test-takers may have varying scores when taking the same test on differing occasions, and although they may have varying scores when taking different IQ tests at the same age – the scores generally agree with one another and across time. Like all statistical quantities, any particular estimate of IQ has an associated standard error that measures uncertainty about the estimate. For modern tests, the standard error of measurement is about three points. Clinical psychologists generally regard IQ scores as having sufficient statistical validity for many clinical purposes.

There might be some bias there but the wiki page gives it a pretty positive review.

According to Schmidt and Hunter, "for hiring employees without previous experience in the job the most valid predictor of future performance is general mental ability."[94] The validity of IQ as a predictor of job performance is above zero for all work studied to date, but varies with the type of job and across different studies, ranging from 0.2 to 0.6.[95] The correlations were higher when the unreliability of measurement methods was controlled for.[7] While IQ is more strongly correlated with reasoning and less so with motor function,[96] IQ-test scores predict performance ratings in all occupations.[94] That said, for highly qualified activities (research, management) low IQ scores are more likely to be a barrier to adequate performance, whereas for minimally-skilled activities, athletic strength (manual strength, speed, stamina, and coordination) are more likely to influence performance.[94] It is largely through the quicker acquisition of job-relevant knowledge that higher IQ mediates job performance.According to Schmidt and Hunter, "for hiring employees without previous experience in the job the most valid predictor of future performance is general mental ability."[94] The validity of IQ as a predictor of job performance is above zero for all work studied to date, but varies with the type of job and across different studies, ranging from 0.2 to 0.6.[95] The correlations were higher when the unreliability of measurement methods was controlled for.[7] While IQ is more strongly correlated with reasoning and less so with motor function,[96] IQ-test scores predict performance ratings in all occupations.[94] That said, for highly qualified activities (research, management) low IQ scores are more likely to be a barrier to adequate performance, whereas for minimally-skilled activities, athletic strength (manual strength, speed, stamina, and coordination) are more likely to influence performance.[94] It is largely through the quicker acquisition of job-relevant knowledge that higher IQ mediates job performance.

I think IQ is a basically just a test that gives you scored position relative to other members of society. Scoring highly on this test tends to correlate with success in life, that is all.