Yes I have tried it several times. I used it as soon as I felt that soreness at the back of the nose which is often the onset of a cold. It always seemed to work for me, but there is always a chance I wasn't going to get a proper cold at all, one will never know. The spray is not particularly pleasant and can leave a burning sensation for a few minutes - but I would give it a try, it certainly can't hurt.
I have also tried it. Again, i would back up the previous answer in that it did seem to work, but you really do need to use it the very first moment you notice a tickle in your nose or throat. Which means it is no use waiting till you get home to use it if the tickle starts when you are out.
So i have one in my handbag, and another at home so that wherever i am, i can get to it quickly.
I echo the above comments.... I always carry one and ensure I don't run out. The one time in the past few years I didn't use it when all around me were sniffing and sneezing and my throat started to itch, was the time I went down with a heavy cold .... and a nasty vicious bit** of a bug it was too !