It's a bit more complicated and requires you to get familiar with Qt's paradigms for things like resource management (I'm still struggling with how to access files outside a qrc), but it offers infinitely more flexibility by exposing the entirety of Qt (and C++) to you as needed.
For example, I wanted to write a frameless app with edge snapping. The two problems I ran across were:
- First, when expanding a window the mouse would leave the web widget and so Titanium would stop sending mouse events (as it should). To fix that I had to wrap my content and center it in a larger transparent <body> and then account for that in the movement code. Ugly, but do able.
- And then, edge snapping on the other hand is impossible. Titanium doesn't handle multiple monitors very well. In-order to get the dimensions of a desktop you've dragged into you have to drop it first and even then it's relative to the upper left corner of the primary display.
I realize these are very specific issues but they're trivial in Qt (I handle resizing and dragging in Qt so mouse position is no longer an issue, and QDesktop is extremely straightforward).
Furthermore, not every library is available in Javascript so it can be useful to fall back to C++. I'm still using mustache.js for templating but I won't be using Strophe.js for my jabber library, I can instead use quicker C++ power library (I'd like to use libpurple but that's a whole other mess itself).
You can easily embedd internet explorer frames in winforms and WPF. If you're using Visual studio its almost a drag and drop affair. To gain things like system wide notifications you will need to use interop to get to the win32 libs, but its fairly straight forward and well documented.
As far as I'm aware (and I'm speculating from articles I've read) is that full support for HTML apps is coming in Windows 8.
EDIT: or just use the other link provided in the other comment which has webkit support :)
