Both the tabbed and scrolling task view layout hide too much information. The Custom Fields and Attachments of the Details tab should always be visible, but they are often hidden by being in the wrong tab or having to scroll down to see if they exist. Attachments are really important!

The fix is simple! Move subtasks, checklists, and assigned comments entirely into the left Subtasks sidebar. This frees up the central area for a clean, single-page view of just custom fields and attachments. Now the task view can display all of the sections/tabs at once with its three-column design!

[ Subtasks/Checklists | Details/Attributes/Attachments | Activity ]

(Enhancements could be added to the sidebar to show more subtask properties, but I don't think that should hold up this change since navigation via the sidebar is so simple when details are needed.)

Similar complaints appeared in comments of these related feature requests: