BEOS may never have been sucessful, but it also might have been had microsoft not actively squashed it. Its nice to try and quarter back last saturadays game, but it doesn't change the outcome.
Its not a strength. Its a weakness becuase no one has stood up to people who insist on needing some silly unque little widget for one application. the linux API is a mess on the desktop. Unifiying the API would good a long way to making more 3rd party developers like adobe get on board with tools like photoshop etc.