These locks are of appalling quality.
I bought two of these locks in August 2009, one for me and one for my wife.
Our bikes are kept in a shed, so the locks are rarely exposed to the elements. I use my lock twice a week, and it is left outside for a maximum of 16 hours per week. The inside of the locking mechanism is already going rusty.
My wife's lock is almost never used outside, as she locks up her bike indoors at work. In January, the locking mechanism on her lock broke completely in the course of normal use. The lock now refuses to click shut properly, and can be opened by inserting any key or screwdriver.
Don't waste your money.