Product review (4 stars): Drip Pro Hose End Timer
I purchased two of these mechanical timers for the 2011 gardening season and they have both worked out just fine.  The Drip Pro's don't feel cheap like the Orbit units found in Lowe's.  The timer knob has a fairly substantial feeling to it when you adjust the watering time.  It's also got a "on-manual" setting on the knob.  My units don't leak when in the "Off" position.

I forgot them outside last winter where they hung from my faucets unprotected from the cold - I live in Central California where we get several nights of freezing temperatures during the winter each year - The units worked just fine when I started using them this spring even though they were subjected to sub-freezing weather. This year they get stored in the garage!

I got the timers for my drip gardening system as well as "hose & low sprinkler" irrigation on a few trees.  Using the timer, I no longer realize that I've left the water running for 2 days on a tree (!) so between the Drip Pro and the timer on my Smartphone, the watering activities in my backyard seem to be under control.

I am purchasing a 3rd Drip Pro today for yet another faucet.