While responding to a question in the Tablet OS Developers' Forum I ran across links to a free 93-page iPad usability report by Jakob Nielsen. (Actually, you may prefer his summary posting if you don't have time to read a 93 page PDF.)
Jakob's comments about inconsistency in the initial iPad apps reminded me of my first concern as I listened to the Fourth PlayBook Webcast. I thought that RIM was being pretty sparse on the guidelines.
I think they've had a year to review the iPad situation and learn from its mistakes, and they would do well to provide more thorough and substantial guidelines. Unfortunately they seem to be too busy with getting the product ready to give due attention to the quality of the user experience.
It seems clear that this lack of guidance will lead to each app being different. Users won't have a clue what to do in many apps, especially those written by Flash-only developers with no usability training, no experience with tablets (since who among us does?), and a growing desperation to get that free PlayBook!.
Nielsen certainly found inconsistent designs among the 35 apps and web sites they used in their usability study. Touching an image produced one of five outcomes, including doing nothing, enlarging the picture, and hyperlinking. I think generally the user was not given any hint ahead of time as to what the outcome might be in any given case. Advancing in a block of text could be done at least three ways: scrolling (with the finger), swiping left, swiping up.
My advice: watch closely other apps as they come out, try to identify the most intuitive, obvious, and effective mechanisms, and try to reuse them in your own apps. With diligence and speed, we can avoid the problems that will doubtless be caused by a lack of adequate design (by RIM) up front.