It might look as the easiest approach and it probably is, if you connect to Windows APIs.
There is a distinct shift towards Linux and now Android OS.
wxWidgets or Nokia's QT are, I think very robust multi-OS platforms and have very good GUI.
I have used wxWidgets based GUI in another language and can say clearly that it is very good and under constant development and support. The latest version is 2.9.x and it is said to be totally Unicode. I don't know whether it is utf-8 or utf-16. It is unlikely to be just LE16 of Microsoft. In any case, there is already a plethera of public domain utf-8 to LE16 and vice versa so wxWidgets would be a better choice because it is identical for Linux and Windows.
The above arguments probably apply to QT as well. Neither of these two have touched Android OS yet, but they are likely to very soon.