Digital Optics (DxO) have recently tested the camera in the iPhone 6 (both models) and have rated it the best IQ (image quality) of any smartphone they have tested—see the following chart.
The 8 megapixel camera in the iPhone with its five element f2.2 lens even knocks out the 20 megapixel camera in the Sony Xperia Z3.
Because of the low-ish pixel count the iPhone 6 has far fewer issues with digital noise compared to camera-phones with higher pixel counts. Due to the lower pixel density there is less pixel bleed thereby resulting in a more vibrate and crisper outcome straight off the sensor.
Hence Apple need to do far less post-processing manipulation of the image to calm down the digital noise and can therefore put more post-processing effort into enhancing the image with less overall destruction of the original quality. Whereas smartphones with much higher megapixel counts have to do significant potentially image harming post-processing to calm down the digital noise, and then they have to try and bring back the focus (sharpening), contrast, and colour (vibrancy).
Apple are leveraging the well known digital imaging law, that, all other things being equal, a lower pixel density provides a higher image quality. This is why the relatively massive sensors in half-frame and full-frame DSLR-style cameras are able to provide the image quality that they do—they have such low (relative) pixel densities.
Also, like the top-end compact cameras and optional on most DSLRs, Apple have put phase detection focussing into the iPhone 6. This should provide faster and more accurate automatic focussing.
So based on the camera the iPhone 6 is a winner. Considering that a third of smartphone buyers in Australia apparently make their final choice based on the camera then this should go well for Apple.
However, one thing I can tell you without any fear of being wrong is that Samsung and the rest will not be happy with Apple beating them on camera phone image quality. You can bet the family pet that Samsung, Nokia/Microsoft, Sony, Motorola/Google, and others in the land of Android and Windows Phone are working 24/7 to try and put together a camera phone to beat the iPhone 6.