I have a 16:10 monitor, and when I play in 1920x1200 the text does not look good at all (lots of jagged, low-resolution/stretched looking lines). It is less noticeable in just plain pictures that do not have sharp lines, but I am sure they suffer as well.
Going down a resolution to 1920x1080 looks great, so that is probably what I will play in and deal with the black lines until this is fixed.
I've only played 2 missions so far, but it's seeming like a fun tower defense game! Thanks guys.