The layout is designed to "stretch" to fit your screen size. By stretch, it means that every cell will attempt to use as much space as possible. More specifically, everything is rendered as tables with the widths set to 100% so that it will fill as much space horizontally and vertically as possible. IE renders columns with as much space as is necessary to display the contents of the column, and then evenly divides the remaining space among the columns, or something similar (might determine their relative size and stretch them so the relative sizes remains the same).
So it's really about the contents of each cell. I designed the included layouts to fill a 1024x768 screen, since this is [or was] a common screen size that most computers could render. On a 1920x1080 screen they work because they just stretch to fill the remaining space. I personally don't think they look good at that size, and to fix it the font sizes should be increased. Using the Auto-size feature will do this for you.
2.6 beta has a setting to turn off the stretch feature.
I have two ideas in the future for layouts. Because coding the layout and layout design is a lot of work, I can't say I'll ever be able to implement them, but they are on the enhancements list. One would be to have a mode in which stretch is not an option, and the layout is rendered not using tables. This would allow a lot more control over the sizing and positioning of the cells. The other would be to take this mode a bit further and release the cells entirely from the structure, and allow them to be placed dynamically anywhere you want (you would specify coordinates). Both of these methods would tie the layouts almost completely to a specific screen resolution (if designed on 1024x768, for example, they probably wouldn't work at all on 1920x1080). But, I think many wouldn't mind this restriction at all. This would probably be very useful for layouts that position cells based on a background image.