According to Apple this should not be a huge ask – underlying iOS code is still iOS – it is just that the interface has undergone a clinical update and a few of the gestures controls changed. Well no it’s not that simple actually.

I spoke to Mic Fishpool, CEO of Sydney based commercial app developer Fish Vision which does apps for iOS, Android, Windows Phone and BlackBerry 10 to get a developers view.

Mic says “The last major change to the iOS interface was to version 5. Upgrading apps was pretty painful at the time involving a week or two work. For commercial, (read saleable) apps it involved changing any fixed pixel X Y sized graphics to scalable vector images. This involved the cost of new artwork using a product like Adobe Illustrator, and a lot of coding. For iOS 7 all the ‘glitter’ is gone and so there will need to develop new 2D compatible iconography as well”.

“It is tough enough to make a living in the app market without OS changes adding more cost” he added.

According to Mic apps that used to look OK on an iPhone and an iPad may not do so now as the Retina display resolution needs to be used as a baseline.

To put this all in perspective there are 900,000 apps that need to be updated and 50 billion downloads to be done again. I am sure Apple never intended for that degree of disruption when doing what amounts to a cosmetic change to the interface and adding some new features.

Developers have mixed views about iOS 7 but two common threads are emerging. Many don’t like the sterile look and many are complaining about the lack of gesture standards and reserves spaces that make it hard to produce versions for iOS and Android, let alone Windows Phone (and RT) and BlackBerry.

Mic says “When developing for Android we have always had to cater for different screen sizes and resolutions as it is part of the coding DNA for an open system - Windows and BlackBerry to a similar extent. But the lack of cross platform standards just got infinitely worse and we will have to build in ‘phantom gestures’ to cover all platforms just to ensure apps can use different interfaces”.

Developers also comment that the vast majority of ‘trash’ apps – the one off, never updated variety that are part of the 900,000 ‘mine is bigger than yours’ iTunes app store will never be updated and should be culled immediately. While no one can accurately predict the cull number speculation is more than 66% of apps won’t be upgraded reducing iOS’s appeal even further.

Other iOS changes mean even bigger headaches for app developers.

An analysis of the smaller, subtler changes in iOS 7 has also alarmed app developers. It seems that the changes requires to be a true iOS 7 app may be a lot deeper than first thought.

I won’t plagiarise and excellent article at Gigaom so I urge you to read itt.

While most of the angst is over the changes to the look and feel hundreds of changes may be needed to cater for changes to how iOS 7 does old and new things.

The new notification system won’t be recognised for start and the space reserved for its ‘swipe up’ will need to be incorporated into previous full screen graphics.

New ways to invoke Face Time and a new feature called AirDrop will change how some apps need to work.

Final word (extracted from various web comments)

• All this effort to re-engineer apps that already worked well just to comply with a ‘fashion statement’
• Going from 3D to 2D flat ICONS — well is that really innovation?
• Downgrade the look of your app to match the butt-ugly new iOS, or die. Great.
• This would never have happened if Steve Job was still around!
• #AnotherReasonWhyImSwitchingToAndroid