Without time tracking enabled, the sub-task list has a progress bar (image from 3.0 release notes) based on how many sub-tasks are resolved.

If time tracking is enabled, you can only track sub-task progress by using time tracking. There is no way to see the simpler "resolution-based" progress bar. Since entering time estimates is optional, I would have expected the old progress bar to still be visible if no time estimates had been entered in any of the sub-tasks.