Value of roof boxes

A follow on to a current topic on fixing roof boxes.

What value have roof boxes?
I ask because we toyed with the idea of having one fitted, liking the idea of putting some of the bulky but not too heavy stuff up on the roof out of the way.
We already have rails, a strengthened roof area and a ladder factory fitted.

We went off the idea when we tested climbing up onto the roof!
Since then we have met 2 people with roof boxes who say that although they have stuff in their box they actually never use it because of the hassle of getting it down and putting it back up.

Any comments?

Gillian