Review of GMAT Club Tests

The variety of questions in the GMAT club tests along with the GMAC free tests is sufficient for GMAT. The quant section of the GMAT club tests I feel is harder than the real GMAT. The best thing about these tests is that they mimic the GMAT completely. The tests are pretty accurate in predicting the scores. I found the filter of question difficulty level divided into 500, 600 and 700, as one of the best features.The explanation to every question in the test is very well put. Can the explanation give a gist of theory or at least a link to the theory that the question caters to? This will help in quick revision of the topic concerned.