I've considered these in the past but opted to not get them.
In the model Erik presented, it doesn't provide the light output (which makes me hesitant).
In RK's version, run time is 90 minutes which can be detrimental. RK - How many did you need? I installed six units master bedroom,top of cellar stairs, top of stairs to second floor, entry hall, kitchen, stair landing. The first time we lost power at night I found out six units was overkill. 2 possibly 3 would have worked well. As far as the 90 minutes goes it take me 20 mins to set up and fire up the generator.
In both, consider the wiring requirements to hang them up near the ceiling where they're supposed to be installed. Unless integrated into a new house, pulling wires can be a bitch. This was new construction
Portability (or lack thereof is another consideration). If not portable, how many do you need? If they are portable, do you want/need to get a chair or ladder out to pull the unit down?
I instead of these (which I did strongly consider but negated for the aforementioned points), I just got a bunch of LED flashlights. Cheap ones are $3.00, decent ones can be had for $20-30. I just put one in each vehicle, each bedroom headboard and scattered others about (in drawers, the shop...). Run time can be upwards of 300 hours on low mode. On their "bright" mode, most are at least 30 hours. I also have flashlights around the house but it is great when you suddenly lose power to have full lights kick in automatically