Cafferty at CNN makes the case, and the economics of the reduced demand are relatively sound. I have a feeling Matt would say no. I'm opposed based on the cost of my time. The general rule of thumb is that you lose 4 mpg's for every 10 mph faster you drive. Let's think on the margin then....If your car gets 28 mpg at 65 mph and hence at 55 mph you get 32 mpg. On a 200 mile trip you would save .892 gallons, which at $3.61\gallon is $3.22 in savings (here is an excel spreadsheet for you to use your own numbers). However, it would increase the time cost of the drive by 33 minutes, which based on the most recent wage statistics is a loss of $11.43.
Gain $3.22, Lose $11.43 if gas prices don't change from that. In fact, gas prices would have to fall by $1.31 from the reduced demand to break-even.
That $1.31 reduction in price is unlikely. It is hard to reduce prices over the long-run by reducing demand in a competitive market (yes, oil and gas is competitive at every point in the production process). The main driver of lower prices is lower costs, which usually requires greater investment, which needs a high pay-off as a reward.