Oh yes it does. Just about any camera can take good shots outside. In low light the Nexus 5 really struggles. In fact, OIS does more harm than good.
The way Optical Image Stabilization (OIS) works is that the lens itself is able to move slightly. So by leaving the shutter open longer, you can let OIS compensate for more subtle hand movement. In theory this works well because a longer shutter means more light gets in without having to increase ISO, which would increase image noise. The problem is that OIS is only advantageous when the only thing in motion is the hand. So if you are simply taking images of props sitting still or landscapes in low light, it works out. But if there is any motion that isn't your hand, OIS's attempted compensation leaves the shutter open longer meaning more motion blur. OIS has this disadvantage in and of itself. What makes it worse is Google's camera app thinks OIS is better than it is, so it expects OIS to do a better job than it will. This means on the software side the camera app thinks it can leave the shutter open longer. But OIS isn't as good as Google thinks. This makes images more susceptible to motion blur than just your standard camera with OIS, like for example some point and shoots with OIS.
Also, the Nexus 5's camera is slow to focus, especially in low light. It takes much longer to focus even compared to my fiance's iPhone 5. Accurate color coming through the optics is also questionable. And Google's noise reduction algorithm is far too liberal in low light shots, and this is not user changeable AFAIK. Plus, video mode does not support tap to focus while already recording.
But sure, flower shots in bright daylight don't suck.