It is a (small) regression to 3.7.10 with intel integrated graphics i915 - but nevertheless :
With an external VGA display (1680x1050) and a closed internal LVDS1 display (1440x900) the external display starts X11 with 1440x900 - for kernel 3.7.x.
With 3.8.2 (and .1) now the external display is driven with just 800x600.