I'm in the process of fixing the Premiere export plugin, and I'm also in the process of writing a corresponding plugin for MSPro6, but neither is done. Plugins for the previous beta will have to be recompiled. The following things are new since 0.3. I've probably forgotten some, and I've definitely not had time to implement some, so this list is likely to expand. There's a new external plugin interface, which will be documented this time.
Some preliminary documentation is available.
There's a new interface which allows applications to use avisynth.dll as a video-processing library, without going through AVIFile or using AVS scripts. VirtualDub plugin filters are supported, via the LoadVirtualdubPlugin command. Convenient Avisynth-style interfaces to many VirtualDub plugins are available in the file vdfilters.avs , which is included with the DLL above. Avisynth filters can now take named arguments. The named arguments can be specified in any order, and the filter will choose default values for any that you leave off.