I've went through a phase where I had multiple subcontexts but realized that was just taxonomy and it does work better to just focus on a Project or Folder if, for example, I want to do only work things on the computer while at work. I do still use subcontexts under Agenda and Waiting For, and all the other contexts are just places. Errands does still include a few specific places as subcontexts, but I find I've even aggregated those into clusters of places that are a few minutes apart by car, separating those in opposite directions from home.
The Computer, Email, offline, etc bit is still not quite right. What I'm trying right now is to have just Computer with the subcontext Phone. I find that for the kind of calls I put into OF, I like to be working from my computer where I have my address book and can source information I need on the call and record any notes--a call is not just about the phone. But sometimes I make those calls while on the road and it's just me and my PDA.
The Computer, Email, offline, etc bit is still not quite right. What I'm trying right now is to have just Computer with the subcontext Phone. I find that for the kind of calls I put into OF, I like to be working from my computer where I have my address book and can source information I need on the call and record any notes--a call is not just about the phone. But sometimes I make those calls while on the road and it's just me and my PDA.