I had a couple of these 'magic' sponges in the shed, which after reading this thread, gave them another try.
I bought a few from poundland a year or so ago. They do work on certain marks and If I used them on every job one sponge was lasting a day or so.
Anyway to replenish my stock, I bought 60 of them from eBay last week and they arrived quickly - and they do work as well but barely last two houses - absolutely crap!
Back to poundland methinks