At our studio we are working with haXe and NME, and the advantages are great. Performance and cross-platform are the more important points (at least for us).
- Even with only a few people in the forums, you can receive a lot of help. It's a very active community. Check at haxenme.org, haxe.org, and haxe group in Google groups.
- Numerous people helped port the many APIs. They can also help you
to do your own.
- If you make a simple game, without many "social" features,
then cross-platform is like doing ctrl-enter in Flash. You can target the following platforms with haxe and NME: iOS, Android, BB PLaybook, WebOS, HTML5 (with some
limitations), Windows, Mac, Linux and Flash.
- The very best of the best: In FlashDevelop for Windows, you can do haXe
projects targeting C++, Java, and NME (a framework that brings flash
methods to haXe). Also, you can use MonoDevelop 3 with a haXe add-in.
It's not as good as FlashDevelop, but it does the work. Another option
can be FDT, though it's not free.
- If you have experience with ActionScript, then haXe won't be a
problem for you. Of course, there are some language differences, like how they handle for loops and iterators.
- HaXe is great if you want to be able to transition from one platform to another, like from web games to mobile games.
- The performance is really, really great. However, we didn't test it
against stage3D. You will need to work with different methods
according to the final target, but it is not a big deal.
- There is not much documentation, and existing documentation is not very detailed. There are only a few books on haXe, many of which are outdated.
- If you are a flash game developer looking for sponsors, then
you'll face some troubles when you need to add their APIs. The same
applies for mobile development (iOS GameCenter, iAds, Google, etc)
- There are times that you'll need to know how to code in native
Obj-C, Java, or C++. BB Playbook also requires a device (I
don't know if this has changed).
- There are not many cross platform IDEs
- We've only worked with single-player games, so I can't recommend haXe
for multi-player. I guess it won't be a problem, but I don't have the
experience to confirm that.
I hope you find this answer useful, and don't hesitate in trying haXe. It is not hard to port code from Actionscript 3.0 to haXe and NME.