Few writers put the kind of thought into user interface that John Gruber of Daring Fireball does, and that shows in his lengthy review of the iPad. It's very much worth reading for his detailed impressions in support of why the iPad is Apple's reconception of personal computing. follow link
Go Back and Forth Fast in Preview
If you're reading a PDF in Apple's Preview software, and you follow a bookmark or an internal link to move around within the PDF, you can quickly return to where you were by pressing the keyboard shortcut Command-[ (that's Command-Left Bracket). Or, you can choose Go > Back.
The command works iteratively, so you can go back to just the previously viewed page or if you issue the command again, to the page before that, and so on. There's also an equivalent Go > Forward (Command-]).
- ExtraBITS for 12 April 2010 (12 Apr 10)
John Gruber of Daring Fireball Reviews the iPad