Not too long ago I wrote a short article about FuelPHP and Composer.
Today I can announce that we have decided to use the current 1.6/develop branch as a composer test-bed, and will gradually replace existing core functionality by composer packages.
We will start introducing 2.0 functionality into the 1.x release train, with a compatibility layer to ease migration. First one up is the Log class, which as of today is replaced by the Monolog library. In the next weeks, more will follow, both by incorporating 2.0 packages and by using external libraries to replace current core functionality.
So if you are using 1.6/develop, make sure to run composer after you next pull!