I hope to be giving you a good news by telling you that I developed QtRaw, a Qt image plugin for raw images, using libraw.
In my blog post there's a link to the source code.
It would be great if more people can test it and report how it works with different cameras. The plugin attempts to be fast, by using the thumbnail when the requested image size is smaller than the thumbnail, and processing the raw image only if the requested image size is bigger.
Since this is a Qt plugin, support for raw files is automatically added to any Qt/QML applications.