Assume that they work correctly, and are correctly supported on all major platforms, not just Windows. No messy plug-ins are required. Maybe you don't want vector graphics badly enough to pay a programmer to implement them for Netscape 5.0. By opening up their product, Netscape has given lots of companies around the world a monetary incentive to improve and promote Navigator. Most importantly, they've brought an opportunity for innovation back to the web.
Nothing's new about that in the computer industry.
There are also reports of XML having been added to Netscape which should particularly interest you. The point isn't that everyone will want to download the source and modify it. After all, most linux users don't modify their kernal themselves. The point is that the people that want to add new features can. Of course, I don't personally plan on using any versions of Navigator except for the Netscape one.