Yes, as greg stated, you will conserve fuel.
With greg's simmer device, heat gets transferred back to the burner which in turn continues to heat up the fuel and evaporate faster. It also looks like it reduces the incoming air which will make the little flames on the inside of the burner get smaller, which in turn makes the burner hard to stay lit. In the case of the 12-10, when it is starts to lose heat, there is a point when it starts to "burp" (excess fumes accumulate to a point where they ignite with a "poofh") so, be aware of that. Having to use a pair of pliers is not user friendly. Trail Designs came out with simmer device but yet to see it on the market or see results posted by those that were sent samples to test.
If someone wants a sample of the ones I've come up with let me know. The response to this new device is low which makes me think everyone has settled in on their own ways of simmering(like greg) and also kinda indicates that not many want to simmer something or bake. This new device is based on the KISS principle. Totally user friendly.