Kevin Drum provides a great explanation of the reasoning behind Fitzerald's decisions. Unfortunately for administration supporters, it has nothing to do with the state of the offense, but with technical limitations of the relevant laws.
The trial of "Scooter" Libby (if there is one, there is always the possibility of a plea bargain) is likely to expose a side of the Bush administration they would rather keep under wraps. It will be impossible for them to deny that Libby lied under oath, and the indictment itself undercuts arguments that Libby was some kind of "rogue" official. It's known that Libby consulted with Vice President Cheney and others early on about how to handle the press inquiries about Cheney's role in sending Wilson to Niger.
The prosecution will on fuel questions about intelligence in the lead-up to the war in Iraq. The Italian angle of the story is finally starting to break. Josh Marshall and Laura Rozen have been covering the role of Italian intelligence officials in creating and disseminating the forgeries as well as the false information that provided the administration with one of the most concrete points to hang their hat on.
Much of the story is bogged down in teasing out the countless twists and turns of how the operation worked, but as the story receives greater exposure, it will also begin clearing itself up. It is certain to be an interesting few months.