I haven't used one of these. But I have owned some related items, so based on the specs, here's an armchair commentary (and we all know what they're worth ;-).
First of all, it's a Freeplay. That generally means well-constructed, good components, good quality battery, quite reliable, and long service life overall.
The only unique feature here is the foot-powered generator. Much more powerful and versatile than hand cranks.
My question is, what would a person use it for?
7 Ah is not a lot -- it's fine for running small electronics or LED lighting, or acting as a buffer between solar panels and applicances. It would turn over a small engine a few times; but 20 Ah is more like it for real boosting capacity.
The battery is a lead acid "gel cell," which is fine for indoor/outdoor use since it doesn't breathe hydrogen. Note, though, you shouldn't try to charge these in sub-freezing temperatures.
It doesn't have an inverter built in (all the offshore competition does); for that price it should have.
The weight comes in at 18+ lbs. That means you're using it at home or transporting it in a vehicle. In either case, you may have access to better charging options than the foot-powered item (solar panel, DC from engine or isolated deep-cycle battery). If all you need is a cell charger, or flashlight battery charger, a hand crank unit would be adequate.
I guess, for me, it comes down to cost. I think it's too expensive for what you get. Except for the charger part, I could build my own for a quarter of the cost.
All that said, though, if lost in the barrens or evacuating a disaster area, it would be endlessly more practical than some things people pack (X-box, budgies). I just wish I could buy the pushme-pullyou generator as a separate item.