Supposedly they intend to deprecate previous versions and one deadline has already come and gone for this - currently the talk is of end of January, though I personally very much doubt that they will go ahead with it, as long as a significant proportion of users are still using the old API.
Briefly, the new API uses JSON, not XML, and it WILL require a big rewrite of all your stuff if you are using it.
The official forum is useless, there are no official responses to bugs, no-one you can ask about anything, there are various bugs and limitations people are running into and in short you'd have to be crazy to migrate with such a lack of information forthcoming - I certainly won't be.
Just wondering if anyone else has any feedback on the migration process, someone who has done it?
The radio silence out there, you'd think no-one was using the Amazon API?! Perhaps we can help each other out here?