Quicken and QuickBooks Pro are both available for Mac. Premiere is still Windows-only, but the database server will run on Linux.
I still think that the biggest obstacle to Apple taking a larger section of the market, is cost. The engineering and software folks at Apple are great, but their marketing/sales people are still asking wayyy to much for their hardware. One way to bypass that, would be to release the OS for use on non-Apple hardware, but I doubt we'll ever see that while Steve Jobs is still alive.
