Excellent compilation of good quality questions

i think the GMAT club tests have a three fold advantage for the GMAT preparation.
1. Wide variety of different questions types. For example, even within a specific topic like number properties, the quiz includes all possible concepts that could be tested.
2. Organized. I think this is an under appreciated benefit. Everything is arranged topic/chapter wise. Makes it easier to test specific topics and helps approach GMAT quant methodically
3. Finally, The analytics are brilliant. I think 50% of your prep involves understanding where you went wrong but also understanding where you went right. The post test analytics help you review your weaknesses and understand your strengths. What it essentially helps you with is preparing a strategy for the final exam.

Net, I think these tests are a worthy investment of time and money especially for the quant section.

I have significantly improved my test scores after practising from these.