I read on the planet that apt-btrfs-snapshot would be available for Natty. The brief description of what it does sounds very nice:

it will automatically create filesystem snapshot (of everything but /home) when apt installs/removes/upgrades. With the apt-btrfs-snapshot cli app its easy to list/remove/rollback the snapshots

But before I convert my entire life to btrfs for the sole purpose of gaining a built-in backup system, can anybody tell me how btrfs's snapshots work. To my layman's brain, it sounds like this would eat a devastating amount of disk space if you're taking snapshots every time you install or upgrade something (I do this more than once a day).

I assume the system is smarter than I'm allowing it but I really don't know. How do the snapshots work?