Walk-thrus and use cases are supposed to provide the client perspective, but as you noted they usually don't communicate the intensity of some seemingly minor issues or the tediousness that comes from using the product day after day.

When I used to direct software development for a company that sold accounting software to CPA firms, I always had a picture in my mind of how the accountants used the system. Whenever I would go on site to visit one of our clients, though, I always learned something new about how the system could be used and what the rub points were.

There's no use case like the real thing.