I recently found Glest in gentoo's portage system, so I thought I might give it a try. I played it for the last few hours now and very much like it, so thanks very much to everyone behind the project!
However, there is one minor (but stupid) bug in the version I tried (glest-2.0.0-r1, gentoo-ebuild from portage):
If you start Glest with a very wide resolution (3200x1200 is my default setup), the image "stops" before the right and left screen borders; some 300 pixels or so at each side of the screen are just black. This problem does not occur if running Glest in 1600x1200.
From what I've seen I assume Glest renders a region outside of the screen when using a normal 4:3 aspect ratio but won't properly stretch this region if using a wider format. I haven't tried using a 16:9-ish resolution, but I guess that might not be wide enough to show the black borders.