I have used these before and don't really rate them too highly as I can always see the shadow line where the positive line would be.
However I did a test at lunch time (CD27) and I could see a really faint line, even the sides of it against the white background, It developed from about 2 mins and I could see it up until about 15 mins after but it seems to have faded now!
I'm going to buy a first response but just wanted to see if anyone had a similar experience with them? and what was the outcome?