I would compare it to a slow scene in a book/movie. Though the viewer may want to rush through the slow bit to get to the action, the build-up of walking makes getting the run power all the better.
A bit of a "hitting yourself with a hammer because it feels good when you stop" kind of thing, wouldn't you say? And there's a difference between slow and
boring; I don't mind slow scenes or slow gameplay
if they work on their own merits.
Recently, I showed Knytt Stories to a 12 year old Taiwanese student. I watched her replay the "Tutorial" level for the first time in ages. Very interesting. The first few screens use walk and it makes the game feel very "real," like Juni is a little girl walking in the rain. I recommend checking out the first few screens of the tutorial again. Very nice.
I never noticed it in the tutorial, but I got that feeling when I was playing
Shipwrecked; I really liked the transition between the initial leisurely exploration of the island and the urgent return to the shore after the appearance of the plane. And everyone cites
It Waits as a good use of enforced walking; it does a good job of magnifying the level's menacing tone, even if it does get somewhat old on repeated playthroughs.
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I guess that I should clarify my position here. If slow movement
enhances a level or a section of a level, either by allowing for a different approach to challenges or by contributing to its overall tone, I'm all for it. But I have little patience for authors who use it because they want to make me focus on the environment itself (
Skyfalls, presumably), or because they think that it would be good as a "buildup" to getting the run powerup (
Infestation, which puts the run just out of reach in the first room, ostensibly as a stronger incentive to get the climb as quickly as possible).