The following is an excerpt from Ars Technology.
As it turns out, the US Department of Energy (and almost everyone else except members of Congress) was correct when they predicted that there would be little energy savings. This echoed concerns voiced after a similar experiment was attempted in Australia. Critics pointed out a basic fact: the gains in the morning will be offset by the losses at night, and vice-versa, at both ends of the switch. That appears to be exactly what happened.
Basically, there's no reason to go through this every year.