The best summary of the Butler Report I've so far seen is Jonathan Freedland's comment piece in the Guardian.
On who, if anyone, the report actually criticised:
Lord Butler did not thrust a dagger into the prime minister or anyone else yesterday. Instead he presented parliament, press and public with an elegant, walnut-encased, velvet-lined box full of sharpened knives. “You might use these,” he seemed to say. “I couldn't possibly.”
His lordship was careful to supply a sheath for each blade, lest anyone suspect he was inciting their use. But the steel was there, the glint unmistakable.
On Andrew Gilligan and the '45 minutes' claim:
Yesterday's report vindicated two important parts of Andrew Gilligan's original story. First, it said the claim was wrong and should never have been in the September dossier, certainly not in the form in which it appeared. Second, Butler nodded to suspicions that the 45-minute line was only included “because of its eye-catching character”. To make the dossier sexier, as Gilligan might have put it.
Once again, though, Butler refused to push the knife in all the way. Surely, a sceptic might ask, 45 minutes was included despite its flaws because it served the government's aim of making the strongest possible case for war? You might say that, implied the peer. I couldn't possibly comment.
In summary:
When he had finished, Butler's audience, like a school speech day dismissed by a kindly headmaster, wondered what to make of it all. It was confusing: some thought the headline was “Blair slammed”, others said it was “Whitewash II”. It might take a while to sink in that Lord Butler had done neither. He did not play the assassin. Instead he handed the PM a bulletproof vest, and the public a set of live bullets. That at least will ensure fair play – and what could be more British than that?