I definitely agree. I think the days of maintaining a unified codebase for multiple platforms are becoming numbered. There is so much more benefit to developing desktop applications to specifically target the OS for which they are being written. Beyond just look and feel, you get the slightly more intangible but exceedingly rewarding benefit of integration. One of the things Apple seemed to really be emphasizing at last year's WWDC was building apps that integrate with the whole Mac experience. I, at least, feel that one of the most important goals of developing a Mac application is to make it feel like an extension of the entire user experience, rather than an individual, self-centric, and marginalized entity.