Interesting that you rate Google Now as high as you do. I've had somewhat counter experiences.
Specifically, both me and a friend decided to upgrade to Nexus 5X's this past month, he from an iPhone 4S, and I from a Moto G.
Since I'm the one who's been using Android for longer, I've been his go to source for questions about the user experience, woe's about inconsistencies, and investigations on getting things done.
What immediately became apparent is that apparently, the voice integration of Google Now seems quite terrible compared to Apple's Siri. I never use the voice features, but it turns out he is highly dependent on them, using Siri to transcribe most of his casual text interaction, control music, set timers, make quick appointments, and look up facts.
However, when he moved to Google Now he found that while Google Now could in theory do all those same things, that it did so quite inconsistently (failing at minimum 5% of the time, up to 25% of the time). I tried and found the same problems.
For example, I'd unlock my screen, swipe from the lower left to activate Google Now and then say "set an alarm for 10 minutes". Sometimes the little jiggling colored stripes would just never start moving, indicating that it didn't even engage the microphone. Other times it would catch what I say and correctly parse it, even responding "Ok, setting your alarm" and display the alarm card. However, it would never actually set the alarm.
There are plenty of other inconsistencies encountered, this is just one that I experience frequently. My friend can go on for quite a while though about the issues he faces with Google Now.
Anyway, has anyone else experienced issues like this one?