I've got the Timex, and would heartily recommend it to anyone. The accuracy seems very good indeed (measured 6.27 miles for a recent 10k race, and 13.25 miles for todays half marathon) It's great for pacing in a race, as it's more accurate than posted mile markers (such as at Windsor today, where they were all over the place), and is brilliant for training runs as it frees you from the constraints of running measured courses. I've run with a friend who has the Nike SDM, and the Timex has been more accurate on every occasion (she gets different readings from her Nike according to what pace she runs at...)
In short, I'm a fan. The worst thing I can say about it is that I've got a white, untanned patch on my left upper arm where it sits!
venom