Now you can choose in advance whether you get a 4x4 or 5x5 puzzle. Finding the current longest average solve time or lowest completion rate is not feasible. The hardest I've seen so far are medium difficulty 4x5 offerings in an hour of play. So, it will still be hard to find the very hardest puzzles with no guarantee they are the hardest. The lowest scores you see are higher than what a really good solvers can accomplish. My math and logic background has allowed me to see deep connections with some of the clues and allows me to extract the maximum information from the others, thus making for fast solve times. Lastly, the best players can get a million points with fewer than 2000 puzzles and only playing less than 2 hours a day. So,if you play while drinking your coffee in the morning and awhile after work or whatever to unwind, you have a million points in a month.