I've been using Simplehuman for ~6 weeks now.
1. I am at 0-inbox a lot more often than before. Given I receive several time sensitive emails, managing my inbox is critical and that has been simpler in the last 6 weeks
2. I really like how intuitive the keyboard shortcuts are. I see myself typing out "gi" in other apps too :P (Did it a couple of times after responding to a LinkedIn DM)
3. Phalgun is super responsive. I have asked him for at least 4 shortcuts and they were all implemented thoughtfully.