Just did the bloody thing today. By the time I finished, I had a splitting headache from staring at a computer screen for so long. But somehow I managed to get a 730 average: QR 720, VR 700, AR 770, band 1 SJ. Doing the test confirmed my suspicions that it's quite an arbitrary test, and doing well relies far more on the techniques you employ than any innate ability. Most importantly, be ruthless about leaving a question if you're spending too much time on it. An easy question is worth just as much as a hard one, and by wasting time on the harder questions you've probably lost the opportunity to do 3 easy ones. Go with your initial gut instinct rather than deliberate for too long, more often than not it's the right one. Also, I'm not sure if this is just me, but the 'progression' type questions in AR are by far the easiest to gain marks on, but they're often near the end of the test, so make sure you give yourself time to get to these!
I think the point of the test is not really to measure intelligence, but how well you can perform under pressure and make quick decisions.*