It is useful, although 99% of what it provides can be ignored. Watching the live view to see how people navigate around can enhance the way you list and even the structure of the shop. As in my post above the location aspect I find vital, I could well of written off many 100's of £'s if I hadn't had that.
It can sometimes show that an item you have that is not selling is in fact the catalyst to others selling (landing pages) - so never underestimate the power of a supposedly non-selling useless listing. To put it another way - if you think of a lot of items that would be desirable to buyers for sale in shop - sometimes a non-selling item acts as the door...... without the non-selling item there is no way in.
So I only use about 1% - the important 1% which can teach me something..