My experience with wxWidgets is that it's full with leaky abstraction... Not really wxWidgets fault here, but the philosophy - they wrap native widgets under common interface.
To give you an example - getting the current line or number of lines from wxTextBox control on Windows might in fact do way more than what you expect (the leaky abstraction) - it sends a message to the control to get size/current line - but what that does internally could be something which scans the buffer over and over - so if you have a hundreth of megabyte window with text (log screen) - you might have severe slowdowns.
Also I've found it very hard to extend with custom widget and make it right. Qt is much easier, while MFC has been the hardest for me. Juce is also easy, and I guess gtk would be too.
To give you an example - getting the current line or number of lines from wxTextBox control on Windows might in fact do way more than what you expect (the leaky abstraction) - it sends a message to the control to get size/current line - but what that does internally could be something which scans the buffer over and over - so if you have a hundreth of megabyte window with text (log screen) - you might have severe slowdowns.
Also I've found it very hard to extend with custom widget and make it right. Qt is much easier, while MFC has been the hardest for me. Juce is also easy, and I guess gtk would be too.