Oh, I think I might have used one or two of those ...

I found them to be good because they can basically confirm the observations you have made for yourself and definitely help with timing. They are also simple to use. The cheapest ones are found in supermarkets and I don't think there's any difference between them and the more expensive brand. I used Seratec once or twice from the clinic but didn't notice any difference in quality between them and the ones I got at Safeway. Like Sal said though if you have regular cycles you are probably only too aware of when you are ovulating but if you need a bit of help to confirm it, the peestick can sometimes be your best friend.

Good luck!