just bought one today for the heck of it. they are certainly bright enough and the beam is fairly isolated so it does not light up a large portion of the cabin.
however, there are two disadvantages. as with any adhesive-backed item, they don't stick well unless it's a smooth flat surface. i stuck one onto the headliner and it seemed like it had a nice firm grip. so i figured i'd check on it tomorrow morning and see if it was still attached or if it ended up on the floorboard. about 10 minutes later as i was preparing some grub, my alarm goes off. what the? anxiously i head out to the driveway to check on the rig. nothing wrong with it. i see two people walk around the corner of our block so i follow them thinking they may have tried to break into the rig. in the shadows, it looked like some father/child combo so i just stopped in my tracks and headed back. i look around the rig - still no sign of forced entry or vandalism. i scratch my head. i then open up the rig. crap. the friggin' light triggered the radar sensor. it's now upside down on the floorboard. so much for the adhesive that "sticks anywhere."
the second disadvantage is that you need to un-stick the unit from whatever it is adhered to if you want to change the batteries. that means you probably couldn't use a stronger adhesive because it'd be a p.i.t.a. to take it off and reapply. granted the leds will last for a while with limited use, it will be an inconvenience when the day comes to change the batteries.
an alternate way to mount these things may be some kind of c clips made of thin metal like paperclips. may be able to poke two into the headliner and lodge the dot.it between them. i doubt it will be a snug enough fit though.
