A nice user interface, at least With all the functional limits and partial implementations of the PlayBook, you would think it was a total disaster -- but it does have a nice user interface, a clean cross between WebOS's concept of cards and Mac OS X's Dock Exposé. The screen is divided into three basic areas you can hide and show: a menu bar at the top you pull down, the central window that shows the apps and their contents, and an app bar at the bottom you pull up to see all apps. Thus, it doesn't take long to get to an app or a control, yet it avoids both the screen clutter common on Android devices and the sometimes too-simplified view of iOS.
The UI isn't perfect, though: It's hard to position your cursor inside text. You have to tap at the right spot since there's no magnifying-glass tool as in iOS or BlackBerry OS 6 to help you see your cursor's position relative to the text as you move. But the selection handles are nice and big.
The onscreen keyboard is serviceable, though due to the small screen, it's nearly impossible to touch-tap. The Web browser, based on the WebKit engine used by iOS and Android, is also serviceable. It has a handy full-screen option, except you lose all navigation except Back in that mode, even though there's room enough to retain the Forward and Refresh buttons. The browser's live preview windows for tabs is sophisticated in the style of Mac OS X's Dock and Windows 7's preview tiles.
Note: Many websites won't know the PlayBook's unique user agent and thus will think it's a BlackBerry, presenting you with the mobile version of their sites. (You can see its user agent via InfoWorld's free Web-based user agent checker tool.) On the 7-inch screen, such "mobile optimized" sites often display awkwardly, and you can bet any Flash content is excluded.
On the bright side, the PlayBook supports Flash, with no need to download a player as on Android. But Flash objects are often slow to load, and some would not function. That's an issue Flash also has on Android, as my colleague Neil McAllister discovered in his extensive Flash tests. It's becoming increasingly clear to me that Flash and mobile don't mix.