Getting my game out still relies on the current Sparrow framework, but is mainly C++ with hooks for talking to Sparrow as is, so that's of no concern and would make porting trivial.
While I've not looked at marmalade I still feel Sparrow's light weight approach and the whole take care of the hardware bit without trillions of lines of code is for me. If of course it ever deviates from that and includes a multitude of things rather than having them as add-on's then obviously it becomes a different thing entirely. But yes, the KISS just supply me with a way to draw things I like. Less is more. I've probably mentioned it before.
As for mention of the Java port, Java is on the lists of things for me to learn as it's another good tool for the box and for distribution luckily it's very C++ like, I still feel there's not a big take up on Sparrow due to its limiting target. Which is a shame as I guess more of the Cocos crowd would come aboard if it was not for that limitation.
But as Daniel points out, this kind of task is fun, which is what motivates me. 🙂
As for a lot of work, the code is damn tidy so that's of no concern 🙂, I've spent many years porting code. The only issues outside the view controller is separating the platform specifics, touch etc.
As for sound I've started using this http://www.shlzero.com/wordpress/?page_id=205 I think it supports everything bar Java.