Undeniably yes. The new compact fluorescent bulbs cost five times as much (less if you get them as part of an electricity company promotion), use a fifth of the power, and last eight times longer. They're already more than cost-effective, paying for themselves within a year of purchase. Mandating their use will drive uptake, and ultimately save everybody money. From an energy policy perspective, domestic lighting is 2.75% of gross electricity usage, so reducing it by 80% would allow us to offset around a year's demand growth. And from a climate change perspective, it would save approximately 130,000 tonnes of CO2 a year - not a lot, but every bit helps.
In short, it's a no-brainer. So why is our government dragging its feet on following suit?