Recessed lighting with compact flouresent is very energy efficient, I am referring to the ones with two lamps and the Alzak reflectors, not a retrofit.
Lighting is not always installed to be efficient. As we all see in our daily travels, there are so many different types of lighting installed it sometimes amazes me.
I have worked for customers who want all kinds of lighting to customers who say install a switched receptacle because they hate lighting (not much money in those jobs). That is part of what makes this such a great country.
If there is a Cheesecake Factory restuarant in your neighborhood, take a look at the varied lighting they install, it is 'enlightening' .
I agree with Tom, we install 100s of these in commercial space and the lumens per watt for compact fluorescents is much higher than incandescent lamps.
The longevity is much greater also.
As for the question of spacing, what wattage lamps, how high is the ceiling, how bright do you want it?
What ever spacing you choose, for even light distribution the distance from a wall to a fixture should be half of the distance between adjacent fixtures.
Bob
edit I was typing while Scott was posting and no I would not want these in my house either.