Qt was really stable for last years, indeed Qt 3.x -> Qt 4.x was a painful migration, but they learned their lesson and Qt 4.x -> 5.x was pretty much as smooth

Qt was really stable for last years, indeed Qt 3.x -> Qt 4.x was a painful migration, but they learned their lesson and Qt 4.x -> 5.x was pretty much as smooth as it gets. For simple apps you can mostly migrate from 5.0 all the way up to 5.6 without changing any lines of code.