Took me an hour to resolve so might as well share to community...

Running a Atom D2700 + GMA 3650 (rebranded PowerVR SGX 545) hooked up to a 1080p HDTV via HDMI. The X11 and browser fonts were so tiny that they were illegible.

The solution is to explicitly set the DPI for X11.
1) Open the Console
2) Enter "vi /etc/X11/xinit/xserverrc"
3) Modify the line from "exec /usr/bin/X11/X -nolisten tcp" to "exec /usr/bin/X11/X -dpi 100 -nolisten tcp"
4) restart