Even libraries like Qt will use win32 ( on windows ) some where inside but it is abstracted away. So why reinvent the wheel? If you don't have a specific reason to work with win32, then you probably shouldn't. Qt is a great library, so is wxWidgets.
I prefer Qt, it's easy to work with, has LOTs of other functionality not just GUI stuff. Also has a cross platform IDE that IMO is second only to VS.