What I love most about Universe Sandbox is how it let's you separate the wheat from the chaff on your Steam Friends list:

1. People who accuse you of cheating because you appear to be 'playing' Universe Sandbox at the same time as another game (or while away from the keyboard) clearly don't know what Universe Sandbox is.
2. People who get the One Hour, One Day, One Month, and One Year achievements on the same day aren't really being all that clever with their hax.

Watching planets careen about like balls on a billiards table is pretty fun, too.