I use them. The light output is minute but still useful in completely dark conditions.
I have about a dozen in total, one affixed to keys, a couple to lanterns, a couple more to flashlights.
Certainly sufficient to find these items in the dark.
After manufacture the light output declines very slowly, they NEVER fail or go out completely if physically intact. After about 12 years the light output is halved, after another 12 years it halves again and so on. Replacement every 10 years or so is therefore advisable.
Do not throw the old ones out, they still give some light but you need several old ones to do much good.
I place my old ones on a high ledge in my bedroom such that they give an indirect light reflected from the ceiling.
Even with dark adapted eyes, the light is not really enough for safe movement but it does help with locating oneself, no question of blundering around facing in the wrong direction.
In the UK these Beta Lights are readily available from suppliers of outdoor goods and are often given away as free gifts with higher end outdoor clothing and sleeping bags, so that the zipper can be located in the dark.
The common "key ring size" ones cost about £5 to £10
I also have a giant Beta Light purchased from fleabay, that gives light to read by ! just if suitably placed.
These products are not easily obtained in the USA due to concerns about them being very slightly radioactive.
auction site link Link shows one of the giant ones, I have no connection with the seller.