Battery life of the 10mW DX keychain is about what you would expect (poor; about 15 minutes). Durability is good, and the button feels solid. Output stability is good (more consistent than my 5mW keychain). Divergence is roughly the same as my other 10mW. Overall, I'd recommend it.
I agree with ProjectX. I'm glad I got this one. The battery life does suck but if you can get button cells cheaply then you are good to go.
It's funny though because I bought a three- pack of Energizer button cells and they didn't last long at all. So then I bought a cheap red laser pointer from Wal-Mart for $2.96 that came with 2 sets of batteries and those cells last much longer than the Energizers. :-?