I’ve gotten in touch with JetBrains, and I secured a license for IntelliJ IDEA for any FlashPunk developers.
I think this is one of the best ActionScript IDEs for Mac (it still doesn’t compete with FlashDevelop on Windows, sadly). You can get a free 30-day trial from their site to see if you like it.
If you’re a developer who has submitted changes or pull-requests to the FlashPunk repository, you’re eligible for one of these licenses. If you’re interested, send me a PM.