Olympus has recently (May 2011) released a firmware update for their DM-2 & DM-4 digital voice recorders. Below is a list of the improvements of this new release.
1. Support the functions of USB microphone or Speaker.
2. Supports the function to register the voice keywords for the schedule.
3. Supports the function to register the voice memos for the schedule.
4. Supports the playback for audio files from the schedule list display.
5. Improve the volume setting when the text file is spoken out.
6. Supports to directly connect the device to CD drive and import DAISY contents from CD. (Only for DM-4)
Olympus has put together a pretty cool information page for the Olympus DM-4, which includes: videos, manuals, updates and more.
Check it out: http://olympus-imaging.jp/product/audio/en/dm4/accessibility/index.html
Verification Source: Amy Leslie, Sr. Product Manager