Having been writing in Haxe for a long time, I think the "Code once deploy everwhere" line is an exaggeration. However, it is a nice framework and has some advantages. In Haxe, you can easily break out into the native language with c-like # compiler directives, so you can do #if platform=ipod. Now, this isn't a perfect solution but it does mean that you can keep a good portion of your code the same source which could save you some time. For certain elements like the UI, though, you probably have to write a custom version for each platform no matter what programming language you use.