I had strips from Access Diagnostics and have been conducting a scientific experiment on them. Here's now it's been going.
af-3 days: absolutely no sign of a line at all
af-2 days: very faint line, if I waited until all the colour had run through and the stick was nearly dry
af-1 day: even fainter line than the day before. But a BFP with CBD.
af+1: slightly darker line, but still very faint
af+3: finally, a line that I could be sure was there and not just my imagination
af+5: this was the first day when I got I line that I would definitely call a positive without any doubt, nice and dark (but still nowhere near as dark as control line)
So, since they haven't given a decent positive until 5 days past my period being due, and since they're supposed to be so uber sensitive, I would rate these stick as a load of rubbish, and certainly not good for early testing.