You have less of an excuse on the Mac, which has literally the best GUI API in Cocoa that anyone has ever invented.

Not so iron, if you have many platforms to manage. Usually it doesn't worth it to manage tons of separate toolkits for each platform, if there is no common abstraction at all. It's just too costly.

If your app looking like shit will cost you significant sales -- as is the case for most productivity and design apps -- then yes, you have to port the GUI bits to each and every toolkit you're using.

Firefox, LibreOffice, VirtualBox and etc. If you don't know how to make good GUI using generic toolkits it doesn't mean it's not possible.

Anyway, if you buy application for its "looks" - there is something seriously wrong already. It should look good, no doubt, but it should be functional first.

>as is the case for most productivity and design apps

Completely the opposite. They tend to provide completely custom, not native looking UIs, and therefore using cross platform toolkits for them only makes more sense.

And I wouldn't describe LibreOffice as "not looking (and running) like shit". Again, nobody on Mac actually uses it, and Windows has the real Office.

And I personally think he's (shmerl) right. Learning a couple almost completely redundant APIs, but each with it's own problems, gothas and plain stupid decisions is hardly a good thing.

Most users know so little about the UI of their computers that they don't know when to click the mouse once or twice.

They spend their day working on Windows, checkout Facebook on their iPhone on the way home, play a game on a Playstation then send some email using Gmail on Safari.

Then you have the major changes within operating systems over recent years, Windows Vista/7 and Windows 8 both introduced major UI changes as has OS/X.

Peoples interaction with computers has become much more diverse. Unless the UI is jarringly different they just aren't going to notice.