The hole cutters are fine in Thermalite blocks on a newly constructed wall. However since you can cut into those with a padsaw or stanley knife anyway, not much point in using the cutter there.
For anything else, there are 2 possible outcomes:
1. The tool is blunted and ruined within 10 seconds. The wall is not damaged.
2. A huge hole is created in the wall, with loose plaster falling out over a wide area, bricks coming loose and the brick you are cutting fracturing into 3 pieces. The resulting mess takes 10 times longer to repair than cutting the hole properly.
The jigs to guide a drill are also useless, since they just help with holding the drill staight and level.
If you can't hold a drill straight, what are you doing using it in the first place?
The best way is to:
1. Place box on wall, draw round it with a pencil
2. If the wall is plastered, use a stanley knife to cut through the plaster just outside of the pencil lines.
3. Drill holes at each corner first, then along the edges, then several in the middle.
4. Use a scutch chisel and hammer to remove the brick/plaster in the middle and to clean up the back/sides of the hole.
For those that don't know, this is a scutch chisel:
