Here's the impression I'm getting from these posts:
1) Players want one movement mechanic that is superior to all others. Thinking about which mechanic to use is not desirable.
2) If they do think about which they'd prefer, and the game prevents their preferred option, they get upset at having to do a challenge.
3) Challenges should be beatable with no prior attempts - failure cannot be tolerated.
I think the trade-off between methods of transportation is great, and am excited to see speedrunners put it to get use. Watching Kazooie talon trot and jump all day does get boring
On a different note, I do agree that rolling down slopes needs to happen. In fact, your speed in ball roll should be slower the steeper the slope is, such that it would make turning at corners of slopes a lot easier to do. That would solve some of the gripes of players overshooting and having to restart their ascent.