I recently purchased an Oven Tamer II. It is well made and works as advertised. It took a few minutes for the auto tuning function to tune the Oven Tamer to my oven, but once that was done it is quick and simple to use. Most often, I just press the on/off switch, and the oven starts to heat up to last temperature setting that was used. Generally, that's 180 degrees. If I need to use a different temperature, just a few button clicks is all it takes. It's interesting to see and hear to oven be cycled on and off every few seconds as the Oven Tamer keeps the temperature within a degree or so of the set temperature.
I've not used the timer function yet, so I cannot comment on it yet. However, for only a few dollars more, I think it is worth having the ability to set the oven to turn off automatically after a set time. So far, I've not needed to run errands while I'm cooking something, so I've preferred to manually turn the oven off. But, I like knowing I can put something in the oven at 9 pm and not have to stay up until it has finished cooking!