aptosid is a distribution based on Debian Sid (unstable), and a very lean distribution as such: It is basically 'vanilla' Debian Sid, but with a custom kernel build and some scripts/patches to ease the potential pains of using the evolutionary unstable Debian branch.
Even though it is based on unstable, it is actually surprisingly stable. Which might seem like a contradiction! 
In my experience it is more stable than Ubuntu, or even Linux Mint.
In this post I'll do a quick review of the distribution, and try to give you a list of reasons why you might want to switch to using aptosid as your new GNU/Linux distribution of choice.