If I had to sum up the gmatclub tests in one word, it would be "Brilliant". The questions, especially the quants section is tailor made for gmat test takers and is intentionally made a few notches tougher than actual gmat questions. This gave me solid practice and built my confidence when I was tackling real gmat questions. Their test taking interface is also very similar to that of the actual gmat which helps immensely. Another helpful feature is the study mode. This lets you practice questions and review them at your own pace. Once you are confident enough you can move to the exam mode. The moderators have done a fantastic job of building this question bank and I would highly recommend buying the gmatclub exam pack if you are looking for a 700+ with a strong quant score.