IELTS, like every other standardized test, is just as much about learning the structure of the test as it is about having a good English foundation. Having one or the other won't help, you need both. If you ask for my honest opinion, all standardized tests are biased and some are just an untrustworthy method of benchmarking one's language/thinking skills.
To me, IELTS felt like the test designers were more focused on tricking the test takers than putting more effort into real assessment. In particular, the listening section is well designed to fool the test taker. Sometimes the conversations happen very fast and in addition the speakers are intentionally trying to confuse the listener to no end. It drove me crazy. In the reading part, there is a lot of confusion surrounding the TRUE/FALSE/NOT GIVEN type of questions.
I got L/R/W/S scores of 8.5/9/8/8 with an overall band of 8.5. Frankly, I thought my speaking test went really well. I am an academic researcher and have given more than 25 talks at national and international conferences.
I can't complain too much because this score gives me all the points one can potentially get for immigration purposes, but the fact remains that IELTS and many other tests are stacked high against test takers. At the very least they should allow people to combine results from different test iterations. Instead you are forced to do well on all four components every single time you take the test.
