No, I kindof have an infinite number of priority levels in some of my systems. Not just two. On my context action lists, things can be written anywhere on a page of paper, with the precise position indicating a priority level.
That works well. I used to do that with Nirvana for about a year (manual sorting), but I found that I only sorted (and constantly adjusted) the top tier reasonably accurately and that the rest became sorted just roughly into a middle and a low tier, but seldom adjusted within those tiers. So I started using another grouping (instead of entirely manual), and this is what has now got me looking for apps that have colored priorities Three levels is just nice for me - normal as standard and then either up or down for the exceptional ones.
If you're willing to share -- can you explain to me what you do when your priorities change? Or do you feel they don't change often enough for that to be an issue?
When priorities change, most often it's a high-priority item being added. This could either be something new, or something already in my system that has had its priority suddenly increased. Either way, I usually take a blank piece of paper, write down an action or project, and put it on the top of my "zero-folder" or on my desk, where I'll see it first. I also have two more inboxes, beside my "zero-folder" (which acts as my inbox), which are almost always empty and which are of higher priority than my "zero-folder" (one higher than the other). I might put the paper in there, or put more than one paper with actions having to do with the new, urgent thing there.
If it's a duplicate of something already in my system, then when I run across the original, perhaps days later, I simply remove it from my system as something already done or as a duplicate, or move it to the top of my pile if it's still not done and I'm not completely sure whether I have another reminder about it.
For some things that need to be done in a short time I use specific reminders such as moving my watch to the other wrist, holding an object in my hand, etc.
If a project has its priority lowered, then when I run across actions for that project I simply move them to a lower-priority folder. I feel no need to find them and move them before I run across them during the normal use of my system.