Pros: It's a cool glowing thing you can put on your keys or anywhere you like.
It should keep glowing for many, many years, as the half life of tritium is over 12 years, and the low energy betas won't damage the phosphor crystals much, so in 10 years there should still be more than half the brightness of today.

Cons: It isn't very bright, I'm thinking of getting some of the larger ones, but they cost a bit more.
You can see the glow if you cup your hands around it, or are in a dark room.

Other Thoughts: I am a nuclear physicist and so when I saw these I had to have one. For those worried about the radiation, tritium is a beta emitter with very low energy (average 5.7 keV). These particles can only travel 6mm in air and 0.0006mm in tissue/water. Thus they cannot penetrate the dead layer of skin. The other reviewer who claimed he measured the radiation with a geiger counter was mistaken. The particles won't make it into the detector. Tritium will produce a small number of X-rays by bremsstrahlung, but they would be very low energy, and absorbed in the plastic container. I couldn't detect any radiation at all from mine with my most sensitive detector.
As for legality, of course I don't know the regulations everywhere, but here in my state of australia, less than 20GBq of tritium in a "gaseous tritium light source" isn't even legally considered radioactive. You would need a volume of more than 0.1 mL of pure tritium and I estimate the 5mm by 1mm container only holds 0.004 mL = not legally radioactive. Even if you were to crack it open and inhale the gas you would get less than 1000th of the radiation of a chest X-ray.

Bottomline: It's cool, but if you want more glow, buy the larger ones

Pros: Nice and small for a keyring
Good build quality - Mine has been attached to my house keys since last August and no problems.
It really does glow :)

Cons: The glow is not very bright. It must be in a dark area to see it.
Only came in a bibblewrap bag (no box) so if giving this as a gift, it looke really cheap and the person will not know what is so special about it!

Other Thoughts: It looks like a cheap glow in the dark keyring, until you see the glow does not dim like other glow in the dark things do.

Bottomline: Useful to find your keys in a dark room!! Might be a bit expensive for its size, but hey it is still glowing all these months on!

Pros: - Interesting gadget for geeks
- Makes finding my keys easy at night when the lights are off
- Interesting talking point
- Should glow 10 years

Cons: - Not very bright, lights have to be all off in the room to see this actually glowing
- After a couple of months of being on my keychain the epoxy seems to be cracking at one end so won't be using it anymore as worried the tritanium will leak out

Other Thoughts: Ok thing to help find things in the dark, but needs to be dark dark not just dim room.
Pretty small too so you need to know what your looking for.

Bottomline: With the risk of it splitting and the tritanium leaking and although I'm not sure how much is this item rather not risk it so not using it any more.

Pros: -It doesn't need batteries, manteinance or charging, it just glows. For years.
-It's really small, can be attached to anything without adding bulk.
-Bright enough to be spotted instantly in a dark room.
-Green is by far the brightest color these come in, closely followed by yellow, then orange, blue and white (dimmest).
-Useful for flashlight mods.
-The vial is 1.55mm x6mm (about 1mm longer than usual).

Cons: -Plastic gets scratched easily with keys and other items.
-Cannot remove the split ring without scratching the plastic.
-It's hard to take out the vial (to use it for flashlight mods), the plastic capsule will be destroyed in the process.
-With time and banging up against keys the plastic will develop cracks at the bottom of the capsule (though the vial is also glued inside, so it won't fall).

Other Thoughts:

Bottomline: Keep in mind these will not light up your whole room! It's about as bright as the minute hand on a wristwatch after charging.
But... attach one to a flashlight and keep it on your nightstand, or a shelf in your garage. Attach one to your keys, and you'll always be able to find them even when you drop them in the dark. Attach one to the zipper of your bag, and you'll be able to find/open it after the cinema's lights are off.