Live 7 or later supports REX files. These can be loaded into audio tracks and will play at the tempo of the Set. REX files can also be sliced to a new MIDI track.
Live doesn't support DRM-protected files and this will probably not change in the near future.
The position of MIDI information like note and controller events changed when exported to MIDI files.
Live opens always with the same old Set.
This tutorial provides information on common MIDI file format questions.
When importing certain MIDI files (*.mid or *.smf) into Live, all MIDI data appear in one track.
Not possible to decode an MP3 file using QuickTime if the MP3 is stored on a network disk.
Live 5 or later versions do read MP3 files. You can't read MP3 files with older versions of Live.
When transferring Live Sets that contain mp3 files between computers...
Live makes no sound after importing a MIDI file. (SMF = Standard MIDI files or *.mid files)