The first thing you see when you unlock your phone is the home screen, and to me that sets the tone of the redesign of the OS; the new color palette, the grid system, etc.
When you present iOS as it is by default, stripped of any third party apps, I would say most reception has been favorable in terms of it being an improvement in design.
The problem arises when you have third party icons showing up. Back in iOS 6, it was apparent that Apple didn't try hard to create a consistency in the colors, and there was no profound grid system for the designs. Short of developers using low resolution icons and/or simply creating horrid designs, iOS 7 was consistent in it's inconsistency.
iOS 7, however, presents a very prominent array of specific colors throughout the OS, with the icons confined to a specific grid system to create a very profound consistency amongst the entire OS as it is by default.
Here is a comparison to convey what I mean:
This is a basic home screen with iOS 6.
Clearly there is no grid system or any attempt at consistency which in and of itself creates a sense of consistency and therefore visual flow.
This, on the other hand, is iOS 7.
The default apps seem to be trying hard to create a visual flow with similar color shades and designs that fit the grid, but the third party apps break that visual flow in a horrible way that, I think, is what causes to make this example look like the "OS designed by a 10 year old".
*source
Here is an example of what I sincerely (and probably naively) hope happens within the first year of iOS 7.
The example here shows co-operation amongst the third party developers in that they confine to the same palette/grid system that Apple used for their default apps and throughout the OS:
*source
All this said, however, reading through Apple's iOS 6 to iOS 7 transition guide clearly shows that they don't see this as an element that could completely put to waste their efforts towards creating a consistent operating system.
Good design comes from consistency which creates a simple and unobtrusive visual flow, not from turning a blind eye to the fact that people will need to download third party apps and have easy access to them.
When you present iOS as it is by default, stripped of any third party apps, I would say most reception has been favorable in terms of it being an improvement in design.
The problem arises when you have third party icons showing up. Back in iOS 6, it was apparent that Apple didn't try hard to create a consistency in the colors, and there was no profound grid system for the designs. Short of developers using low resolution icons and/or simply creating horrid designs, iOS 7 was consistent in it's inconsistency.
iOS 7, however, presents a very prominent array of specific colors throughout the OS, with the icons confined to a specific grid system to create a very profound consistency amongst the entire OS as it is by default.
Here is a comparison to convey what I mean:
This is a basic home screen with iOS 6.
Clearly there is no grid system or any attempt at consistency which in and of itself creates a sense of consistency and therefore visual flow.

This, on the other hand, is iOS 7.
The default apps seem to be trying hard to create a visual flow with similar color shades and designs that fit the grid, but the third party apps break that visual flow in a horrible way that, I think, is what causes to make this example look like the "OS designed by a 10 year old".

*source
Here is an example of what I sincerely (and probably naively) hope happens within the first year of iOS 7.
The example here shows co-operation amongst the third party developers in that they confine to the same palette/grid system that Apple used for their default apps and throughout the OS:

*source
All this said, however, reading through Apple's iOS 6 to iOS 7 transition guide clearly shows that they don't see this as an element that could completely put to waste their efforts towards creating a consistent operating system.
Good design comes from consistency which creates a simple and unobtrusive visual flow, not from turning a blind eye to the fact that people will need to download third party apps and have easy access to them.