Hi Sonia, I have used the Nexus One, Nexus S, and Galaxy Nexus. The cameras on all those Google phones are terrible at low light. Especially my current phone the Galaxy Nexus.
All the reviews that I have read on the Nexus 5 suggest that the camera has not improved. There is the HDR mode which takes better pictures but that's not the default mode. And that means 90%+ of people will not see the improved pictures. If something is not the default setting, it will not get used by the vast majority of people.