I have been using Blender quite intensively for Flight Gear model developpment (for more than 5 years now) and I have run into trouble while migrating to v2.57.
Flight gear uses ac3D files as its native file format and the import/export script has not been ported to 2.5.
I'd like to know if it is in anybody todo's list to do so or if the internals have been so messed up that it would be impractical for me to try to port ?
All this knowing that python is definitely not my language of choice, but after all, open source lives on contributions so I may give it a try

If all of this fails, is there an exporter to at least port my messed up files back to 2.49 format so that I can continue useful work until 2.5 gets somewhat more usable for my purpose ? I must admit it was an unpleasant surprise to discover there is no backward compatibility for the file format.
As a side note, the knife tool is definitely a regression compared to 2.49 for my modelling activity. Most cuts are polylines rather than free form, and a lot need axis constraints (machines are simple geometries after all). I've seen fixing the knife tool in the todo list so really that is not my point. Please just tell me that the fix is coming soon !
Regards