What's so great about it? Well, it collects all lines of communication for support in one place and attempts to provide automated help for your request where applicable, while you wait for a representative. The biggest improvement, though, is that the site lets you track the progress of your support requests. This includes tech support emails, billing inquiries, and yes, GM tickets. You can edit your ticket while it's in the queue, track it, and even update your ticket and place it back in queue after it's been closed if you feel it wasn't addressed properly.
The full text of Blizzard's announcement is after the cut.