I downloaded the SDK and Simulator for the Blackberry Playbook today. A few quick notes about my experiences so far.
The first thing you should know if you are on a Mac is that you must have VMWare Fusion in order to run the Simulator at this time. The site notes that you need to download VMWare Player (this is a windows and linux only product).
The simulator is pretty bare bones right now, it doesn't even include the web browser yet.
Blackberry is providing a nice promotion for developers to start building apps for the playbook. If you build a PlayBook AIR app and get it approved on App World before the playbook is launched, they will give you a free PlayBook (this offer is no longer valid).
Another thing that caught me up was the developer mode password on the playbook simulator, however I got it right on my second guess (the password is password, my first guess was empty).