Jordi Boggiano released first Composer beta. Yes, we've used enldess alphas before! That means more stability and some new features. My favorites are the following.

composer show now displays installed packages only, not all the packages available. By adding --tree we can get a nice installed packages tree. With composer why we can learn about why certain package was installed. And with composer why-not it's possible to get an idea why certain package wasn't installed in certain version.