On the other end, as a user, I greatly prefer desktop apps, because I don't "lose" them as much. It's easy to lose a chat tab between lots of browser windows+ta

On the other end, as a user, I greatly prefer desktop apps, because I don't "lose" them as much. It's easy to lose a chat tab between lots of browser windows+tabs. A single IM window is harder to lose. And then there's the integration: both look&feel and functionality can make a huge difference.