When I'm on my Nexus 5 home screen the phone should be listening for "OK Google", but it doesn't. I'm running snapdragon batteryguru. Could this have turned off this feature? Any way I can see what batteryguru has turned off?
In addition, after setting Language to U.S. English, you'll get lots more information than if you type in commands via it's region specific settings.
I used to despise Siri, conversely I love and use Google Now daily.
It rapidly continues to become more useful the more you use it. After just one week it's a very impressive tool for more uses than I would have imagined. I can only imagine how great it will be in another month.