Drupal 6 does not handle non-local files well. That means if you want to use something like Amazon's S3 file service you are pretty much out of luck. Media Mover got around this by overriding some templates but the implementation did not work well for extensibility and left most use cases in the dark.
Ok so I totally missed my deadline of January 1 for Media Mover 2. Fine.
The alpha is actually nearing- this time I mean it. The selecting files from views works, auto generating images for imagecache (multiples all at once), full Drush support, unlimited actions per step, FTP module has been completely rewritten and does a better job of auto linking FTP content (by users, by directory, by token) then it did previously, the number of modules has been reduced to make configuration building easier, configurations in code, the API is new and simplified (and easy to upgrade to!) and so on. Hey, the interface even got an overhaul which makes it feel more like Views, and so on. Yes there are probably lots of bugs still. There is no upgrade path from Media Mover 1 and won't be until the bugs are not serious.
So here is some of the pudding. This is the new admin landing page which lists all of the configurations. Here you see three different types of configurations- disabled, overriden from code, and normal- built from the admin interface. What is no longer here is the notion of child configurations- with configurations now having unlimited steps it seems unnecessary to add the complexity of having the child configurations. Selecting files from an existing configuration is still possible so I'm going to argue that Media Mover 2 offers more possibilities for building configurations despite lacking this feature.
As Media Mover 2 finally moves toward alpha, I've taken the risk of doing some significant refactoring- or at least improvements- to make the transition to Drupal 7 easier as well as to provide a much more robust platform people to start leveraging.
Similar to Drupal 7's [hook_file_load](http://api.drupal.org/api/function/hook_file_load/7), Media Mover now offers hook_media_mover_file_load() and hook_media_mover_file_save(). This allows for easy altering of files as they pass through the system. These are both cache aware so you can still benefit from caching while having the ability to avoid modifying a cached file if your modifications are not dynamic (cached Media Mover files have $file->cached set). Steps and configurations are also alterable on load and save.
Media Mover 2's S3 implementation now supports private files hosted on Amazon. You can set access to files by role- with the obvious exception of the anonymous user. Links to each file expire after a set amount of time which gives site administrators a degree of control for providing protected content.