The Verge spoke with Google's Director of Engineering for Android, Dave Burke. Among the issues that were seen on the phone initially were slow focusing, "too little contrast, too little saturation, and too little color (or inconsistent color)." Focusing was so slow that The Verge called it "absurdly" slow.
According to Burke, some of the issues were because Google focused (pun intended) too much on image quality, and not on speed. He said,
There’s a tendency to say, "oh, we have this cool thing that stabilizes, so lets make the shutter time longer, reduce the gain even longer, and get better shots."Those better shots, though, meant frustrating shooting speeds when the camera was used in good light.
The app itself launches a full second faster than before, and there is also a new progress indicator in HDR+ mode. HDR+ image capture is, by necessity, longer, but the progress meter helps understand what's going on as the photo is taken.
Google is not done yet, either. It's been known for some time that Google is reworking the Android camera APIs. Among the changes coming is RAW format support. As far as the Nexus 5 goes, more tinkering might be in order. After all, as Burke said, "Cameras can be pretty complicated."