I like the old incandescent lights.
A few years back (2006) I thought I'd do my part for the environment and replaced all the lights in my house with compact florescent lights (CFLs). After a while I began having sleep difficulties, dull headaches and a hard time seeing. I attributed the problems to other reasons... mostly job stress and ageing.
Last fall we painted and bought a new TV stand for our livingroom. For some reason it just looked really off... very cold/harsh. I replaced the lights in this room with regular old incandescents and the room looked better. I also noticed that my eye strain went down and I'd get tired in that room sooner. I eventually replaced all the lights in my house with old school incandescents and I now go to bed earlier (between 10-12pm when I used to regularly stay up to 1-2am), my headaches are gone, and I can see better.
My guess is that the colour temperature of the CFLs is what caused this. The lights are a lot more blue than the red tone put off by incandescents. I'm guessing that this threw off my prehistoric brain's clock causing my sleep problems. I'm guessing that all the extra blue light through off my colour contrast, which made it very difficult to see different shades, leading to increased eye strain and headaches.
Anyway, that's my story. I'll never willingly use another CFL again, although after seeing that LED lights have different colour ranges I will be willing to give LED technology a chance once the price becomes a little more reasonable.