First one, might be a bit ambitious but super nice:
1. A searchable list of plugins (look at how the Firefox project did it). I would love to see this included in the actual program as well with automatic install but great to have it on the web page as well to "show off"
2. Simple download. The download button should stand out more in my humble opinion since if not the main feature of the page at least one of them. When clicked the download page should basically tell you exactly what to do from when you click the download link to when you enter the program + give you links to "getting started / first time user" tutorials. This to show new potential customers how easy it really is. Needed if this is to become a paid application. It would also be nice to be able to easily access a list of previous releases.
3. Large fonts. With tutorials and general help sections readability becomes important. Design for easy reading. Big fonts but not too big.