CFL's, LED's, or some different form of technology is the answer,
I do find the LED's used for traffic signal's better to see, than incandescent lights, I have also found that some versions of CFL's give better light than other versions. I recently purchased a GE 6 pack of equivalent to 100 watt bulbs, and then some GE CFL's which gave off a whiter/bluer tent. The 100 watt conventional cfl's worked best in larger areas, while the more expensive white/blue tint looked gave strange shadows until all the bulbs were switched. The best advantage to using CFL's is that you can get more light from a signal fixture, the worst part is they are either on or off, and you have to purchase new modules to use them. The LED lights sound interesting and I have seen some uses of it, but it is it dimmable, and how does it compare to incandescent and CFL.
The Mercury concern with CFL's is about the amount of mercury released into the ground water when one is thrown away. Their are two two types of fluorescent tubes, ones with mercury and the ones without mercury. Industries have to properly dispose of the tubes containing mercury. The problem is that CFL's contain mercury and are being thrown away with traditional garbage, and the mercury is infilltrating landfills.
It would be great if x-10 would manufacture their own bulbs, but instead we have to realize that x-10 was based on older technology, and it would be unlikely for them support newer energy saving technologies.