Ah, the increasing difficulty level makes a difference. Though for purpose of proving skills, it seems you could just skip to the harder ones, even though that may not work well for training.
They are not monotonically harder, and they are not all the same exact skill being tested. So someone who has completed Project Euler problems 1-30 has done more to demonstrate her ability than someone who has only done Project Euler problem 30.
If your level is such that 30 represents your current challenge, then doing 1-29 won't take toooooo much time anyway. And you can still have fun trying to improve on the best solution offered so far for the problem -- there are multiple ways to solve a given Project Euler problem.
I just got this random idea that people who want to become better at life could benefit from a common scale of "leveling". No, I don't mean vague Lesswrongey things like "changing your mind". I mean a set of concrete criteria like "you qualify for level 2 if you can do 5 pull-ups, have solved 30 Project Euler problems, and did 10 cold approaches". Obviously there would be separate ladders for different character classes, but not too many. Also obviously, my example was a bit too high for level 2. So I guess I really want to ask some meta questions here:
1) Do you think agreeing on a common leveling scale would be a good thing for a substantial subset of LW users? Would you feel good about leveling up and telling other people about it on LW?
2) Is there some good way to determine leveling criteria that are neither too high nor too low? Maybe make an intermediate scale of "experience points"?