It is absolutely real for me. I've got like two closets full of older but perfectly fine stuff (like the laptop I replaced with the laptop I bought this year) that I would feel bad throwing away but I don't want to bother selling through normal means (and none of my immediate friends is interested in having).
I would absolutely use this service to get rid of the stuff even if the offered price were marginal. In my case, I'd even be fine shipping the stuff out for free if the box shipping were pre-paid (but I may be an extreme case).
Having too much stuff is a first world problem, for sure, but sign me up.