I agree that data density is by far the biggest problem with the current design (which is beautiful). Building on what others have said about the second line (notes, context/project, defer/due), I find that it not only wastes space but also makes the lists much less readable. Instead of just being able to skim the text on the left to see my action titles, that text is interspersed with other text (context/project) of a completely different sort. It makes it very hard to skim — I have to try to filter out the contexts/projects as I try to focus on the important content.
I would love to have a "high-density option" with only a single line of text. I would also love the ability to go further and hide the context/project title entirely from the tasks view. I find contexts primarily useful for filtering, but once I am looking at a filtered list of tasks in a perspective, I don't need to see the context for each task. Being able to turn off the context/project indicator would make the lists more readable and allow a single-line, high-density view without being overly cluttered.
It also might work well as a per-perspective option, so that, for example, I could set my "Phone calls" perspective to not display the context for each task since they all, by definition, have the context "Phone."
