Good discussion, thanks for posting. For the replaying levels thing, I agree with the point that playing easy parts is fun and it also makes you better, but I still get frustrated at replaying easy parts that I have played so many times when I just want to complete the part I died on.

In fact, especially on those old Mario platformers, replaying a level many times not only brings tedium, but it also imprints the feeling that you suck so bad to be doing this over and over again.