I use it to check the temp in the morning before I leave the house.
I keep an eye on the low temps, so I know when to leave the faucet in the basement dripping.
I check the humidity in the house in the winter (awfully dry with forced hot air).
I can tell which rooms in the house are notably colder than the rest.
I use the atomic clock to set my watch and for the clocks in the house when the power goes out.
I have a La Crosse:
http://www.lacrossetechnology.com/7391ud/index.php