I was with hastings direct and yes it was very harsh.
Thankfully with a more powerful car acceleration dont rev as high; but the box monitors harshness of acceleration. Braking was bad -there were times I'd come home to scores as low as 20/100 and I couldn't tell you what had caused that; I'd barely touched them. In the end I had to coast, use the hills on sliproads off motorways, go down in gears etc. to slow the car down. If you did ever have to slam the ankers on it was always a 0 for the day.
Same with the driving after 10pm or before 6pm; it didn't go down in increments, just dropped to a zero. And if you had the misfortune of being driving as it ticked over to midnight you got zero for two days.
And as for the bonus miles: I started with a 10k limit (the maximum hastings allow for new customers). You didn't earn "bonus miles" but halfway through the year they gave me unlimited mileage for good driving.
My original quote was £1.5k vs. £2k for not having the box; so thats why I had it. At the end of the year my discount for good driving (scored 95/100 over all) meant my renewal was £500 -huge saving theoretically; but I got lower quotes than that through the usual price comparison sites -without the suicide box.
I'd never recommend anyone to have one. Its definitely negatively effected my driving. Instead of being alert, aware of your surroundings and concentrating on spotting hazards, your attention is always on attempting not to be penalised. And it makes driving far more stressful and tiring, again diverting attention and reducing concentration and awareness.
Like I said before, I felt like I was spending more time staring at the speedometer than the road. I really noticed the difference when I was driving other cars, I was undoubtedly a safer and better driver, and driving was no longer stressful and exhausting.