I'm surprised by where people are focusing their criticism of Magoosh's math tutoring, that the questions are 'tricky', too difficult, etc. What distinguishes Magoosh from other services, in my mind, is that it best explains how to approach the questions in a methodical, systematic way. This service is about test preparation, and Magoosh tries to give you the best strategies for tackling the GRE, not just the best imitations of the questions it expects you to encounter.
Though I also found the math practice questions difficult, this doesn't factor in heavily in my evaluation of Magoosh as a whole. You should be taking practice tests from various services anyway, which Princeton, ETS, Manhattan, etc all offer for free.