I love Nirvana
I love using Nirvana. It works so well for me. I live on my iPhone/iPad and use a desktop computer and have found it works really well on all three platforms.
One simple area that I can share with Nirvana. My Weekly Review used to take me one hour, and really I needed more, when I used Evernote as my capture tool. Now with Nirvana my Weekly Review takes no more than half an hour. Why? I think it's due in part because of how easy it is to navigate through my system. My projects, when active, appear in my Next Actions so they are in plain sight and easy to work with. It's as though an entire step is saved on the Weekly Review because they are tied into my Next Actions.
It's also super easy to work with on the mobile devices.
All I know is the systems I used before didn't make things flow nearly as well as it does now.
iPad, iPhone, MacBook, PC; all running Nirvana, iCalendar and GMail
Mastering Workflow (2012 & 2013)