I have two halogen heaters and find them very useful for giving instant heat for a short while.
Like all portable electric heaters, they are expensive to run. One bar costs around 4p an hour. Howver, the heat really is instant.
They are lightweight, easy to manouevre and give a very cheery glow. In my opinion - the best of the portable heaters available.
I would be very wary of using them if there is a possibility of them being knocked over by small children or animals. Or if they could be touched by small children - they do get hot.
But if you need instant warmth for an hour or so, they are excellent.