04-03-2011 08:40 PM
As John implies the choice depends on your target platform, and to some extent target audience.
If you want the broadest market for your software, then BlackBerry smartphones running RIM's brand of Java ME would be your best option. You've a market of over 50 million BB users, but no Playbook users in the near future. And whether there's a long term future is open to debate (and the vagaries of US patent law). Still the market is far bigger than for the other technologies and will most likely remain so for at least a couple of years.
If you're not too worried about current market size and simply want to code for future products, then Adobe Actionscript/Flex or WebWorks are your two options. Both having the advantage of being useful for other platforms.
And if you want to write games or low level stuff on the Playbook platform, then you would need to wait for the Native Development Kit, which will be in C or C++ (apparently). At some point in the future, this code would most likely also work with newer smartphones (QNX on phones 2012 perhaps?)
In theory you should be able to run BlackBerry or Android apps on the Playbook using "players" that are yet to be released and have only just been announced (and therefore probably won't be of real use until later in the year).