To be honest not good. Halogen bulbs are only good for heat, the dont generate the light in the spectrum that plants need.
well they got 1500 lumens each and were very bright when i put them in. but they burnt two of my plants so i took them out
As tplat says, halogen lights are too hot and in the wrong spectrum. It's worth changing to all CFLs for veg.
i'll confirm that halogen are the opposite of grow lights. they are the wrong color spectrum for growing (the plants can't synthesize the light) and they put out a lot of heat, and heat should be avoided from a light because it is supposed to be kept pretty close to the plants