I had 50mb free, ran apt-get upgrade without devel or testing enabled, and the *official* packages, of which there were about 100 or so, bombed out due to insufficient space. I call this a defect, as an end user who simply opens the box, gets it online, then runs apt-get upgrade will see it fail and end up with broken *system* packages.

Furthermore, the typical end user won't know how to recover from this, either manually or through a reflash..