In essence, the correct way to set them up is so that the drop back arm sits just underneath the spool, with the line gate clipped on and set to a vertical position - this is critical, and offers the most sensitive set up. The rod sits on the back alarm, pressing a sensor which allows the alarm to work. This means that, when you have a run, lifting the rod will immediately disable the alarm as the sensor is released.
A bite is indicated when a pull bob the line releases it from the line gate, allowing the drop back arm to fall. A single tone comes from the alarm - and this is key for pike fishing as it means that the fisherman is forced to check things, rather than just leaving it when there's only a single bleep on standard alarms. Pick the rod up, the alarm stops, and you hopefully hook and land a fish.
I have found them to be very sensitive, releasing under the slightest pressure. Volume and tone buttons help distinguish between the two set ups, and handily, the alarm and drop arm both light up with a run. Overall, I'm very impressed - I have a feeling the negative feedback is due to incorrectly set up alarms. Here's some pics -