It looks like iOS 7 is certainly causing motion-sickness and nausea in a lot of people. And it's not entirely baseless. It disheartens me to see insensitive debate around this issue by a lot of folks, but let's not get into this right away.
Users have been reporting motion-sickness after prolonged use of iOS 7 on their iPhones, iPads and iPod Touchs. On blogs and website covering this issue, comments have varied from some folks reporting nausea after using iOS 7 and several others saying nothing of the sort was experienced by them.
While some users are quick to dismiss this on various grounds, the effects on iOS 7 can actually be nauseating and motion-sickness triggers, especially for people who are sensitive to any quick motion. What's surprising, though, is that we had absolutely zero reports about motion-sickness during all the months leading up to September, between which we had several betas of iOS 7. Is it that the developers are immune to this sort of a thing?
3-Dimensional Effects And Gamification
In my opinion, Android has had a gamified interface much before iOS jumped on the bandwagon. However, the key difference in iOS 7 is the 3-dimensional level of animations and effects. There's actually a lot happening in terms of activity – especially with the physics engine working overtime to deliver gamified animations.
May be it would have had a minimal effect if it had been limited to X and Y axes. Adding the third layer has introduced all the zooming-in, zooming-out, spinning, bubbles jumping up, squeezing in… there's a lot happening. And for users who are not comfortable with a lot of motion, it can trigger nausea. At least, that's what seems to have happened.
Absence of Control Except Parallax
Unfortunately, the only thing you can control/disable is the parallax effect on the wallpaper.
Settings → General → Accessibility → Reduce Motion → and turn ON Reduce motion. This turns off parallax but that's about all we can do at the moment.
Every other animation stays. Apple has not provided a control switch to toggle this. Nor has it provided a way for developers to provide a control toggle. Instead, developers can either choose to use the API (for these effects) or not.
The Internet Sensitivity
But of all the things, this was the worst (not unexpected or shocking though): scores of users who have apparently not been affected are trolling the web, claiming inconsistencies, inaccuracies and errors in the reports. These insensitive users even go as far as suggesting that it's an illusion or a false-claim.
Motion-sickness is a real issue that many face. Only, it's the first time that a technology-related product is held completely responsible for it. People feel nauseated reading books in the car/bus – this is no different. Only, this is totally digital.
Alternative Physical Solutions
Since we don't have a proper solution yet, the best thing you can do will be to regulate your use of the iPhone/iPad running iOS 7. Unfortunately, at this moment, Apple has stopped letting users downgrade to iOS 6 but it's worth giving a try.
To do this, you might have to use a TSS Server (like the one from TinyUmbrella) and then use iTunes to custom-restore to iOS 6 IPSW file. (Hit up this website to select iOS 6 firmware for your device).