I began GTDing back in 2008, after our first son was born in 2006.
Evolution and value of GTD contexts
The landscape has evolved since David Allen published the first edition of his book. There's no big deal for contexts like @Errands, @Home or @Office, which are pristinely clear and quite unambiguous. But much of our work takes place in the digital sphere, with 24/7 connectivity at our fingertips.
That's why so many believe GTD contexts are dead, overtaken by current reality.
But context serves as the first filter you should apply when choosing what you can do at any given moment in time. It's a focus tool allowing you to pay attention to the task at hand while discarding (albeit not losing) everything else. You wouldn't want to go through a single next action list with 100+ items every time you think what to do at any given moment.
Likewise, it doesn't make sense to go through a @Computer list with dozens or hundreds of actions.
GTD contexts and friction
Where do you organize a reminder that you can act on using your @PC, @Laptop or @Smartphone?
Don't you feel like PC/Mac, laptop, email, Whatsapp, Telegram, calls/phone overlap so many times? Some people advice to subdivide your @Computer list according to the tool/app you're using. I don't find that hard to switch between 2-3 apps/tabs in my browswer to perform and finish a particular task. Especially being proficient with the keyboard and shortcuts.
Think about those actions you have to do on your home computer —@Home or @Computer?—, or those calls you have to make while in your office —@Phone/@Calls or @Office?—. @Calls/@Phone, even @Agendas/@People are not what they used to be, since you can reach many people nowadays via a videocall and not a regular voice call. We even use our smartphones for things different than calling or receiving calls.
My current implementation
What if you used some secondary subcontexts to filter, adding the second and third GTD criteria to choose what to do, that is, time and energy? That's my current approach (not always easy, though:
@Computer-Fast: Computer, Low energy/focus, Short time
@Computer-Zombie: Computer, Low energy/focus, Long time
@Computer-Focus: Computer, High energy/focus, Long time
If you were thinking about it, there is no way you'll get a high focus in a short period of time.
You can do anything, but not everything. —David Allen