If it works nicely, that means in the short term that Dell is in big trouble, as are all other PC manufacturers. It also means that Windows may be making some more money starting out, as a decent number of Apple users *may* go out and buy a copy to install on their Macs. However, over time, if Apple plays its cards right and doesn't screw things up, people will see that booting into OS X runs more smoothly and is nicer than booting into Windows, and we may see more switchers than ever before.
Of course, the real key to this would be if Apple would just go ahead and release a version of OS X for PCs. I think with Boot Camp, Apple just threw down the gauntlet and within a year, they'll take the fight to the desktop PC. I cannot wait.