We use these on a regular basis. They are great at cleaning around intricate parts such as alluminium hob burners in combination with wire wool.
They are also good at cleaning behind elements inside the oven where the element enters the back of the oven as it is very difficult to clean stubborn dirt behind these, especially when the element does not drop down or pull out.
Also they are good at brushing down cast iron hob supports especially the corner sections.
3 brushes bought from a DIY store will probably set you back about £4. We buy ours from another store for 80 pence as we get through a lot of these.