Here's the message I got:
As previously published, the NBME has developed new software for USMLE. The NBME software, known as FRED, will replace Prometric's software for delivery of the computer-based components of the USMLE (Steps 1, 2 CK and Step 3).
FRED is likely to replace Prometric's software at testing centers during your Step 1 eligibility period. (Please review the updated announcement on the USMLE website at http://www.usmle.org/news/testsoftware.htm.) This transition may take a few weeks. Because it is impossible to predict whether the FRED software will be operational on the day that you test, it is advisable that you become familiar with both delivery systems. You should also continue to monitor the USMLE website for additional information.
The sample test materials using the Prometric and FRED software are available on the USMLE website at http://www.usmle.org/orientation/menu.htm. If you are unable to download the information from the website, a CD is available at your medical school.
From the sample cd I got it didn't seem too different. You have a column on the left with list of the questions with "i" next to each unanswered question or a check next to marked questions. This makes for quicker navigation, rather than having to click on "item review" to get to the list. It's different enough it's worth downloading it from the link above and checking it out. I think I like the newer format better. You can mark items like before, but you can highlight or strikeout text, including the text in the answers. You can also annotate, though I doubt I'll use this feature much. Rather than have a picture next the the question block it looks like you'll have to click on an "exhibit" button to see the accompanying graphic (radiograph, path image, etc.), though. I'm not sure I like that.