I think there are two possible points to be made with fps in Zelda: the sections which are consistently 20 fps, and the sections where there are lag spikes when you do certain things (swinging a burning sword around, ragdolling an enemy, etc.).
On the first point, I personally think it would have been a shame for Nintendo to have compromised on their artistic vision for the sake of locking 30 fps. I do understand some people are sensitive to low fps in games, and if this impacts their enjoyment then I sympathise, but it's not something that annoys me -- I think I spent too much time being impressed with how beautifully-designed the forest regions are to really notice the fps at all. I guess I don't have the kind of eyes or brain that 'feels' fps in the way some other people do. If it bothers you, it's absolutely a valid criticism - of course it is - but I don't personally really grok how significantly it could impact someone's enjoyment of the game, because it's obviously not the experience I've had.
On the second point, I think you have to expect occasional lag spikes in a game this large with this varied a player toolkit. I'm not a games developer but surely it would be far too difficult to try every possible player input scenario in every individual 'zone' of the game to ensure nothing pushes the engine too far? That being said, there is a certain story-important mountain area that Jiggles mentioned that has almost-non-optional Moblin fights that do lag the game if the Moblin ragdolls start sliding down cliffs after they die, and I think this must have been a rare failure of what is clearly a quite extensive bug-testing process. It's fine to point out that bug, of course, but I think it would be good balance to also mention that Zelda is remarkably glitch-free in other respects. You only have to glance at Bethesda's games to see what a really buggy open-world game looks like.
I'm glad that the debate on here has been pretty balanced. There are people out there are summing this up with shrieking nonsense like "ZELDA RUNS LIKE GARBAGE", presumably because "Zelda has occasional fps drops, rare & minor bugs" doesn't bring in the clicks.