Web UIs can be used with my screen reader's search functionality and quick navigation keys. For example, in Spotify, which uses a web UI, I can do ctrl+ins+f, type rock, press enter and I'm focused on the Rock playlist. Similarly, in Skype, I can search for "audio call" etc. Some elements can also be reached pretty quickly with navigation keys. I think it's much easier to screw up a win32 gui than a web app. The non-web paets of Itunes are a good example. They're accessible, but all objects need to be reached by pressing tab, and there's a lot of objects. There's no semantic structure and no way to provide one. A website-like document would work better in this case.