Halogen lights

I suspect the subject has been brought up before so I will apologize in 
advance for replowing old ground but while we are talking about light 
sources, what about halogen lights?  They can be dimmed, cost very little 
and are a very very concentrated source of light.  The main down side I 
can think of is heat and I have no idea what the lumens/watt numbers are.

At any rate, Ace hardware just had a sale where you could get a 500 watt 
unit that looks a little like an oversized auto heatdlight for under ten 
bucks.  Any comments on halogen lights would be appreciated.

--Earle Hamilton from northern Michigan where coral once grew