Speaking from personal experience: The virus inserts a line of code at the bottom of every web page, which gives the user a download prompt. This will automatically give you the readme.exe file, which will not do anything until opened. If the user hits 'cancel' That is all they get (At least that was all I got from my own website!). If they click OK to the download prompt, I'm sure something worse will happen.
Please urge all of your users to update their virus definitions immediately. Norton and Symantec came out with a quarantine last night, and a fix that will clean a majority of the infected files this morning.
This was truly a nasty outbreak that had my company partially paralized for almost 24 hours.
Tina