I've had some very good experience with Qt, so I would definitely recommend it.
You should be ware of the licensing model though. If you're developing an open source application, you can use the open-source licensed version free of charge. If you're developing a commercial application, you'll have to pay license fees. And you can't develop in the open source one and then switch the license to commercial before you start selling.
P.S. I just had a quick look at shoes. I really like the declarative definitions of the UI elements, so that's definitely worth investigating...