Rainbow Moon Vita development gripes on PSN

Having announced that the lovely-looking Rainbow Moon is coming to the Vita a while back, there's now a chat up on PSN with the usual back and forth, but one interesting point about the cross-development:
Have you enjoyed developing for the PS Vita? 
Marcus Pukropski: Well, we haven’t finished yet! To be honest, I thought it would be easier, because lots of people said the hardware was very similar. But in the end there were so many differences in the operating system that we practically had to re-write most of the engine. And that of course takes more time.

Which sounds like Sony's promises of easy code portability might not be quite what developers were expecting. Any other devs care to share on this one?