As some of you probably have already seen on Mark Shuttleworth's blog, Canonical is embracing Qt. They have even started developing apps in-house using it, such as Unity-2D, which is great.
Within KDE, we've long espoused the idea that the user doesn't care what tools the developer uses and that we should be working to give them the biggest and best choice of applications that work together well. Seeing others, particularly groups who have historically taken rather heavy-set stances that worked against that, start to come around more and more to the idea is good for Free software and our users.
There is still work to be done, however. Mark suggests that Qt developers should start using Canonical's Qt add-on libraries for things like dconf so that Qt apps integrate properly with Ubuntu. This is not that much different from saying that Qt apps should just use Gtk+ for rendering so they fit in better, just doing so at a different layer in the stack.
One of the great strengths of Qt, and something that KDE benefits from greatly, is portability and the wide availability of common infrastructure as a result. We've done a lot of work to make Qt and KDE apps work well on all sorts of platforms. This has taken the form of Qt Platform Plugins, porting Oxygen to other platforms, dialog button awareness, Qt's NetworkAccessManager and much more. Part of the "much more" has also been standardization, of the "weak" sort where it's more about conventions and sharing than strict ISO/ECMA-style standardization, of tools and protocols in use, often aided by freedesktop.org.
To get applications working together as well as possible, the answer is not to start creating Ubuntu-targeted versions of Qt apps, but to work on the issues below the application developer's line of sight. If settings are an issue, then there are two avenues that should be pursued: identification of which settings ought to be widely shared and identification of management processes that ought to be shared. The former can be approached through standardization if nothing else, and the latter is probably a technology problem.
Solving this means working together, not thinking that we are individually capable of coming up with the best ideas ever and that the world should simply bend to our whim of the day. That is a strategy fraught with risk and is socially unrealistic given the number of stakeholders.
There are ways to fill in remaining gaps such as configuration related issues that are well within our combined reach, and which we remain quite motivated to continue to fill in. KDE has led the way in not just helping define standards (including ones Canonical now uses), but adopting ideas from the outside (just look at all the freedesktop.org initiatives KDE Platform 4 uses!), working with others on specs (including things like integrating dbusmenu with StatusNotifiers, something Canonical and KDE worked on together to make happen) and working to improve the mechanisms by which such standardization happens. We're open and wanting to work with others, and Free software users would benefit from as many in the Free software ecosystem adopting a similar approach.
As more groups warm to the beauty that is embodied in Qt, I hope that the message of working together (rather than dictating, for life or otherwise) also spreads. That mode of operation is what got Qt and KDE Platform, as high quality developer tools, to where they are today. It is what motivates us to look at the development platforms we build for application developers and ask ourselves, "How can we make this as painless as possible for the developer while giving them access to as many platforms as seamlessly as possible?" It's a way of thinking that helps create a superior result, and we're always looking for new ways to expand the benefits it brings.