I'm planning on creating the whole game using Adobe Flash, with the mobile versions being publish with Air. I may even do a downloadable desktop version, also using air.
I would be lying if I didn't admit that a major reason I'm using Flash is because I'm a professional Flash developer, so AS3 is a language I'm completely comfortable with. I know that I can build complex engines with it and I know it can take it.
The other reason is that I'm using Flash, and a reason why I personally think Flash it one of the best choices for building apps, is that I can produce an android, ios, web and desktop version with the same unified codebase. I'll obviously have to do some different UIs for the mobile vs the normal size version, but hopefully nothing too onerous as long as I enforce some strict apis. For me this is a huge deal. Even if I spent the time learning objective C or java, like lots of people have suggested I should 'for when Flash dies' there's no way I'd be able to do multiple versions in different languages. Flash means that for the main game elements I can develop for the flash version then just rebuild the other version without having to worry about getting all the changes carried over, because there will only be one codebase.
The only thing that remotely worries me about doing the game in Flash is the saving the game aspect. In theory it should be easy - I can use sharedObject, which should be able to save whole complex data objects. In practise in a previous project I've found sharedObject to not be %100 reliable. I managed to fix that issue by converting everything to primitive data type before the save, then back again, but it's not something I want to do if I can help it, and I'm hoping the issue has been fixed (it was infrequent enough it may have just been one flash player build.)
I briefly toyed with the idea of learning, then doing the it using HaXeNME, but in the end I decided I'm probably already biting off more than I can chew, so best not compound it by adding in a new language, especially one that's so niche and new. If I run into problems I'd be worried about finding answered, and anyway I don't see myself getting more work on the basis of knowing it.