I find you just get a tiny black band top and bottom when watching a 16:9 source on the 16:10 monitors.
As for movies being 16:9, most movies are 2.35:1, but some are 2.4:1. A few are 16:9, but I'd say at least 80% of my DVD's which claim to be 16:9 are actually 2.35:1's letterboxed onto anamorphic 16:9 dvd's. Other 16:9 movies are often just hacked down from 2.35:1 to full screen 16:9, by chopping the sides off. They dont even bother to pan and scan on those, so I prefer the full widescreen letterboxed movies personally.
The difference in picture size when viewing a 2.35:1 movie on a 16:10 instead of 16:9 is tiny, and most DVD playback software will get the aspect ratio correct automatically, if it doesnt you can normally override, and correct it. Its just not a bit issue.
So the argument that movies are 16:9 is pretty much a non issue, 16:10 is a more practical shape for close up computer work, excellent for photography, desktop publishing (2x A4 full size, + space for toolbars etc)