Update: the current update has made it unplayable. I lost several lives just trying to start a game.
First, what I like. The game itself is fun. The options to play head-to-head with friends or random opponents and to play against a group or individuals in "speed rounds" are great. I also like the design and information in the profile.
Now, heres what I think needs work: the questions are repetitive and, as has been noted by others, have a lot of mistakes: A lot of spelling and grammar errors, some questions in wrong categories, and too many incorrect answers, which is unacceptable. I am not convinced of the effectiveness of the question submission process. Though requiring 85% acceptance rate is a strong criterion, it is still open to too much subjectivity. I have only submitted a few questions, but they are in limbo because voting stops after a period of time. I have more to say about it, but I dont believe that the people who can improve the game actually pay attention to these reviews, but I will still make the following comments. My fellow users need not read further, though I do ask that you give more challenging answer options. Too many obvious choices. Kudos to the player who caused this speed demon to incorrectly select "Henry Forcl" instead of "Henry Ford."
Too many generic questions, not enough genuinely trivial questions. You will lose players quickly.
Too many niche subcategories predominate, for example, SpongeBob, the Ninja Turtle Renaissance artists, periodic table, male-dominated sports, American-centered history, or, more accurately, 1960s history textbook questions.
And if developers are still reading, here are final suggestions. Give a game back to the winner of a group challenge. Make sure people can keep the game despite being at the max. More points for achievements and get more achievement incentives. Hire question consultants(I volunteer, for pay though!