When I was in TTC forum, I know there were mixed reports on these. Some ppl said they got a result 7dpo and some said they never got a + on them when they were pregnant.
My personal experience is I used them every month for about 10months and never got a + cos I didn't get pregnant. The month I got pregnant, I used an early one (10mIU) the day before AF due (11dpo) and got a negative. Then the day after AF due (13dpo) I used a tesco hpt (normal 25mIU) and got a +. I then did a digital later that day which was again positive. So I only used one early hpt on the month I fell pregnant, so cannot really say if they completely dont work or just dont work as early ones. Wish I'd used one after I'd got + on others then I'd be able to tell you more.
I do think though, that if you are a POAS addict you are better to used ebay cheapie ones as it'll cost you a fortune if not. And maybe keep some shop ones in the cupboard for if your AF is late.
Good luck and hopefully you will get your +hpt soon.