I would recommend reading Plasma documentation on why traditional widgets are not enough for "contemporary" UI development. http://techbase.kde.org/Projects/Pla...aysOfThePlasma is a good start. Don't know what was behind Maemo 6 UI but to me Plasma's arguments look quite close.

I have seen many commercial applications for Windows done with and without Qt. Trend there is certainly going outside of capabilities of traditional widgets provided by "standard" UI toolkits.