Although I think that in the first lemmixplayer you could go frame by frame forwards (and not backwards) my experience is this:
When solving the origininal dos game long time ago, I solved all levels without using the keyboard and - if I remember correctly - without pausing.
Part of the experience (pain and pleasure) was the fact that it was not possible to correct one little mistake.
The game is not only "knowing the solution" but also "having the skill to execute this solution". Maybe a comparison with a musician can be made here
The level "Mind the step" - one of the last mayhem levels - is no fun at all, knowing you can rewind a few frames.
You have to feel the depths, and know that one slip causes death.
And being able nowadays to play each level without having solved the previous ones also substracts some pleasure of the gameplay in general.
When I would rewrite the lemmixplayer I probably would do this:
cheating levelcodes NO (really solve them all)
frame by frame option NO
skip 10 seconds YES
