Works already ...

I already use the dust magnets rather long. I use a matching handle, on which the cloth is wound up by the matching grooves. (. Does the starter kits) Before using the cloth on the handle is a bit shaken: 1) to produce static electricity and 2) to the cloth "inflate". While dusting I shake the cloth every now and again by. Thus, it sucks the dust better.
From my own experience I have to say, we must not expect miracles from the cloth (the advertising also exaggerates like ;-)). Small, hard to reach corners are ever passed over and the dust is located. I can see that for example in the bookshelves when I take out a book for a couple of weeks. At the spine, on the shelf is dust.
For large, smooth surfaces, however it works great! - Furniture, electrical appliances, lamps, etc. can be very easily remove dust. Be careful: The Staubmagnet works only with a slight, very thin layer of dust, which is loose!
I use the dust magnets regularly 1x a week. One wipe then for two ca.15qm offices (bookcases, shelves, etc.), 1x lounge (books-film shelf, furniture, electrical appliances, lamps) and miscellaneous (such as in the hallway mirror, bedside table in the bedroom, etc. ).
A great advantage over a normal duster is handling. A Swiffer dust magnet is very much more practical and easier to use than a duster.
One disadvantage is the higher price.