If you instead just show a description of the current task, users will want to know how many tasks are left. if you tell them how many are left, they will revert to thinking of it as an overall percentage.
i'm a fan of "checklists" that get ticked off as the process progresses; possibly with progress bars for specific tasks, if they have a straightforward way of measuring that (like % downloaded). but i almost never include an overall progress bar for a multi-step process. it keeps the user's focus on the current task, while still providing some information about what's to come.