That's not to say that there aren't (or won't be) parts of other tablet interfaces that are better than iOS. But trying to convince large numbers of consumers that your interface is better than Apple's -- even when it is -- is a tough sell.

Unlike the iPod, the iPad was the first significant tablet in the market and had the field to itself for the better part of a year. No mainstream tablet has managed to undercut the iPad's price and it's unlikely any will, given the .

There are about 65,000 tablet-specific apps for the iPad. The BlackBerry PlayBook is scheduled to launch with 3,000, but my colleague Melissa Perenson says many are . There are more apps that will run on Android tablets, but the number that aren't just blown-up, fuzzy versions of smartphone apps is vanishingly small.

But Apple's app advantage is temporary, right? With more Android tablets, the reasoning goes, there will be lots more Android tablet apps. Maybe. But app developers have an awful lot of choices to make right now: Do they develop smartphone apps for iOS, Android, Windows Phone 7, WebOS? Do they make tablet apps for the PlayBook, the iPad, or Android options? At some point, it just becomes too much and developers are going to opt for the platform that has the users. And among tablets, that's clearly the iPad.