I think it has a lot to do with your expectations going into the purchase.
I have use of a low-output light. Theyt are very effective in pitch-dark conditions. And the run time of these things is pretty amazing. Last winter, I put a couple used, heavy-duty AAs from a light I bought in 2004 into this my Nite-Ized 2AA Mini-Mag. I use the light everyday, sometime for a half hour or more and it's still going, although dimly.
I never cared for the pattern of the stock Mini-Mags I've owned for decades. For me, the Nite-Ize was a definitie improvement in usable light. But in the daytime, it's hard to tell if these things are even on.
I must be clear, however: These lights are NOT a good deal if
you buy the Minimag and then the Nite Eyez as an add-on ( I did this a couple months before I found this place. For ~$13 you can do better.