I've used them. It will show up as tracked quite quickly but when, or if, it is paid depes on how long the company take to pay them. You will find a guide to that against the company's name. Sorry I don't use the site a lot but it does have forums where regular users might be more specific.
I use Quidco, particularly for insurance and have so far not had a problem - but I know it is quite common. You do have to be careful to follow their procedure to ensure it tracks, ie. clear cookies before proceeding. This makes sure that your purchase is credited to Quidco and they therefore get their cut so that they can then pass it on to you. Hope all works out for you, it is definitely worth doing!
Not sure Spandex. Did you log in to Quidco, clear cookies, go through to More Than and then apply? If so, you should be OK.
CherryChapstick - Quidco is a cashback scheme. If you buy something after going through them you are entitled to money back. It costs £5 per year but this only gets taken off any money you have earnt through them. When buying something on-line I always check to see if they are listed with Quidco, (there are other cashback sites available but I only use Quidco), if they are then I clear cookies then go through Quidco to earn cashback.
When buying insurance I always use moneysavingexpert to see which search sites to use, do a search and then see if any of the cheapest are listed with Quidco. Last year I got £45 off both my car and home buildings insurance, so saved hundreds off what I would have paid with my existing insurer!