We've just added a new feature to tedium that I've wanted since before any of the code was written.
One of the problems I have with the whole Getting Things Done philosophy is how it focuses on what you've got to do. Err, isn't that the point, I hear you ask? And you'd be right. However, as a result of that, it's easy to get disheartened when, as soon as you've finished one task, you look at the seemingly never-ending list of things still to do.
Focusing on what you've still got to do is fantastic for organisation and productivity, but at times I find it saps my motivation. And without motivation it's hard to achieve much. The lists are great for forcing yourself through such motivation dips, but you won't be doing your best work and I find there's a limit to the type of task I can finish when in such a mood. Small, boring or admin tasks can be tackled, but it isn't always useful to ignore the more important fish.
I think that having some indication of your progress can help to boost your motivation. There might be 100 miles yet to travel, but if you've already put the first 2763 of the Cannonball Run behind you then you're on the home straight and those last hundred will take on a different perspective.
That said, we didn't want to provide a boring basic task count. "You've completed 131 tasks" may be factually correct, but I don't believe it's as fun or inspiring as "If each task were a stride, you'd have run 100m". Thus, the brief accomplishment phrase that you'll find at the top of each tag list or on the "My Tags" page is in the latter style.
We hope it brings a little more fun into your doing things, and if you've any suggestions for new achievement phrases we can add to the list then please let us know. It's very tricky to come up with a sentence for every number...