I at least disagree with you. I found they helped me from moving from novice to proficient. That was quite a few years ago tho and I wonder how much increasing CPU has meant you don't hit the ceiling of brute force taking excessively long, which forced you to program more elegant solutions.

What I found most appealing about them is that they're a 1/2 hour task at most, nice bite-sized challenges.

And from what I remember, admittedly only doing the first 20 or 30, while some of it was mathematical manipulation it also forced you to do things you might not be so comfortable with, like recursion or even simple things like storing the primes in an array so you didn't have to check all the numbers again.

It also made me feel more confident when the 'ideal' solution was either the same or practically the same as mine. And invariably if it wasn't you'd learn a new language trick.

Then again I was always very comfortable with maths and would invariably spot any mathematical manipulation 'trick' immediately, so perhaps I'm a bit of an outlier. Although I never went past A-Level standard (18).