I've always been a little frustrated with applications that don't support 16:9 content or don't support it very well. Many applications have traditionally started by assuming that video fits within a 4:3 area and then 16:9 content gets letterboxed within that area (or in worse cases just stretched).
Not so for Windows DVD Maker. We've made sure that 16:9 content is a first class citizen. You'll see from the screen shot below where I've added a 4:3 video file and then a 16:9 video how the 16:9 thumbnail shows up as expected as a nice widescreen thumbnail. It gives me a warm glow inside to see all those extra pixels :-)
You'll also notice that all our DVD menu styles fully support 16:9 as well.