I love 'em!
Not only does it keep food from getting pushed down in filter flow, it keeps it from getting near the filter flow in the first place. In fact, it keeps it from going all over the whole surface of the tank.
This also makes gravel vacuuming much better, too, since all the gunk is confined to one area. Granted, there's other stuff everywhere else too (like fish 'waste'), but most of it is kept in one place.
Even if you use sinking food (like I do for my Ottos and Cichlids), it still goes directly down from inside the barrier, rather than if you were to let it get 'thrown' around by the filter flow.
They're only a couple dollars, so unless you're drastically destitute, it's not really much of a loss
On a side note, you do need to wipe them off ever so often, since food does stick to the tops when you sprinke. But it's still not so bad a gadget to have!