The test provides an amazing insight on the current level of your performance. I suggest that one should go through all the answers that are available in this forum.
If one starts practicing the test at the same time as their actual gmat, it would be really useful. if one can match the test conditions , then an actual feel of the exam can be felt.

This practice test is the closest it can get to the real one. Its adaptive like the real test. My friend who took the gmat said that the score variation with this exam and the actual is at max 10 points.

So yea, its an amazing product