The basic idea behind Particle Code is to write once and deploy eveywhere and the language you chose to write your code is up to you. The code will then be compiled to native code and packaged as apps for:
- Windows Phone 7
This looks like a great idea and has the potential to save hundreds of hours porting an app between devices. However, even though Actionscript is supported, it is a completely separate platform to Flash/Flex, you will not be able to write a Flash Platform application with Particle Code.
Looking at the Particle Code API, it looks fairly similar to the way you would develop apps in Android, you can use Java or Actionscript to create your apps, though I suspect more will be added to that list.
From a Flash Platform developer perspective, there are lots of things missing, MovieClips, Sprites etc. plus you won't be able to do any E4X. You will undoubtedly need to write more code to get anywhere close to the animation capabilities of Flash, but the amount of platforms you can deploy to, may justify that extra effort.