I've been playing in lovely 16:10 since last summer. Not flawless, but works fine. (sometimes, between missions, the map view will remain in 16:10 while the menu around it is in 4:3)
From graphics.cfg:
DisplayMode
{
resolution = {1024, 768};
bpp = 32;
fullscreen = 1;
aspect = 1.333333373;
Interface
{
resolution = {1024, 768};
bpp = 32;
fullscreen = 1;
aspect = 1.333333373;
}
Simulation
{
resolution = {1600, 1000};
bpp = 32;
fullscreen = 1;
aspect = 1.6;
16:9: aspect = 1.777777778