This is so much cheaper than all other sensor cleaning kits I've seen online that I wasn't sure what to expect (equivalent kits seem to be more than £40 normally).
Anyway, I noticed that my sensor was fairly dusty (if you want to check yours, set it to the smallest available aperture, e.g. F22, and take a flash picture of a white wall; any dirt will show up on the picture). Then I made the schoolboy error of trying to clean it by blowing on it. If you're tempted, don't bother! Turns out that you can't avoid getting moisture on the sensor if you do that (even if you blow through a piece of cloth, which is what I did...), and the moisture leaves marks as it dries, making a worse mess than the original dust.
So I used a couple of these cleaning pads, each with a few drops of cleaning fluid (which you get lots of), and managed to remove all the marks. You can press reasonably hard on the sensor, the pads just bend so it won't get damaged.
There's a very small piece of dust I can't seem to get rid of, but it's not visible unless you're using a really small aperture.
All in all, considering the price, this is great. I'll buy more when I run out.