Track lines in git HEAD have changed to thin white lines which makes them unintelligible. It used to be red.
I made a quick hack to resolve that: http://paste.lisp.org/display/320289
and found out that the thickness is what's slowing down rendering of lots of gpx tracks,
0 makes things usable, but with 4.0 panning and zooming is unbearably slow.
While I think the change to white thin lines was inadvertent, it would be a good idea to be able to configure color and thickness.