Like this a lot! especially the live update example on the website. I think we are beginning to see how web developer tools that are browser-based make certain things possible that would never be possible with native tools.
Yes there are many...for instance visual layout driven web development is one obvious example.
I know people who prefer native tools always get defensive about the idea of the browser becoming the default platform for web development (and possibly software development in general), but I really don't see it happening any other way.
The ways browser tools for instance can use the browser itself to help simplify web development is something native tools are never going to be able to do. For instance I envision being able to integrate the debugging/developer facilities built into the browser directly into my browser-based developer product without much heavy lifting.
I may be bias given that I am a founder of a startup (see profile for link) building a browser-based developer product...but I have also spent years working with native IDEs including attempting to build my own IDE (http://bit.ly/IwZCEL), the browser advantage is just apparent to me. Granted there are still improvements to be made to browsers in order to bring them to parity with native environments for software development in general but I think it is just a matter of time.
Though working with QML in QtCreator has been a pretty streamlined and effective experience for me and for web development, at least right now (ie like you say, this will improve in time, in which case you may well be right) I see browser tools (eg the debugger) as a part of a much larger toolchain (editor, REPL, etc).
Though you can build a native editor that has, for example, webkit embedded to augment what the tool can do. Or do something like LightTable which is, AFAIK, build on top of an embedded browser. I think a hybrid approach gives the best of both worlds. Then again, with the trend of everything moving into the browser, I guess this shouldn't be necessary in the future.
