I’m still trying to use Google Inbox as my main interface to Gmail. However, I had to remove the Android app because it killed my Nexus 4’s battery by late afternoon. According to the Android battery usage utility, the Google Inbox for Android app accounted for 34% of all battery use today.
Interestingly, the Google Inbox for iOS app does not appear to be creating any extra battery drain on my iPhone 6 Plus. So, I’ll continue to try it there. But, it was jettisoned from my Nexus 4 as soon as the phone had enough of a charge to boot back up.