Blackberry have some great info on how to develop applications for their new Playbook HERE but it uses Adobe Flash Builder. Which you have to purchase at a significant cost from Adobe.
You don’t have to use Flash Develop, you could use a plain text editor. But it is a very nice IDE to write in and does give you syntax highlighting. And it can compile the SWF file for you. You still have to create the batch file to launch your application into the virtual Playbook, but you can add that into the project and run it from there.
Good luck with your coding