There are a number of significant benefits and features:

Courts can allow registered attorneys to file documents 24 hours a day, 7 days a week.
Reduction of paper, photocopy, postage and courier costs.
Full case information is available immediately to attorneys, parties, and the general public through the Internet. This includes the ability to view the full text of all filed documents.
Attorneys on the system will receive email notices electronically in CM/ECF cases. This greatly speeds delivery and eliminates the costs to both the court and attorneys of handling and mailing paper notices.
Multiple parties can view the same case files simultaneously.
Since CM/ECF uses Internet standard software, the out-of-pocket cost of participation for attorneys is typically very low.