I started using Nirvana back when you could buy the lifetime subscription (I am not sure the lifetime option exists anymore). I remember testing the app, loving it and subscribing it for life! But at the same time I was obsessed with my Calendar and started testing Trello with Google Calendar integration. Long story short, I moved my system to Trello+Google Calendar+Google Keep and started scheduling tasks like crazy. Then I realized I was complicating my system and creating a sense of task urgency that was overwhelming me.
I looked back to Nirvana and loved it again!
Nirvana is simple, pure GTD-oriented with no calendar integration that usually made me schedule everything. So I'm using Nirvana for all my next actions (I love the Areas of Focus option, I have Personal and Work), minimal contexts (@home, @work, @calls, @errands) and everything else that has a date goes to my Google Calendar (reminders, events, deadlines). I use the "Scheduled" option on Nirvana for deferred actions, as a trigger that I need to get back to it again, not as a hard due date.
I store MPN (master project notes) on Onenote and support material on Onedrive.
It's been working well so far!