Just to give you an idea, one single hockey puck halogen fixture with no dimmer mounted to the ceiling (wood cover)of a 10 gal tank produced over 95 deg as measured on the floor of the cage within just about 30 seconds. So you see, they are small but really crank out some heat.
The light from halogen bulbs is very pleasing to the eye. Just to reiterate what was mentioned by junglehabitats, you're not supposed to touch the bulbs with oily hands and you can't jostle the bulbs alot when they are heated if you want to get long life from them. If you simply mount them and leave them be, they last a long time. They will heat the surface they are mounted to as well, though not excessivly. Replacement bulbs are available for a cheap price.
A dimmer is necessary, as alot of ON/OFF cycling where the filament cools down (i.e. like with an ON/OFF controller where the OFF time is more than 10 seconds) will result in shorter bulb life. With a dimmer, they last a very long time, very long.
I've mounted them on PVCx, but I put a disk of aluminum flashing between the fixture and the PVC to help sheild the plastic from residual heat. I doubt I needed to do that, and the PVC didn't get too hot, but it was quite warm. When dimmed down a bit it was definitely fine.