Former controller of BBC editorial policy Richard Ayre has called the resignation of BBC director general Greg Dyke a "seismic shock".
Greg Dyke was at the BBC for four years
He said Mr Dyke was popular and many programme-makers would be shocked to see him go.
The National Union of Journalists said Mr Dyke should not have gone at all.
"He should have stayed to fight on behalf of BBC journalists and put in place the processes that are needed after Hutton's findings," it said.
But Labour MP and the BBC's former head of European affairs, Chris
Bryant, said although the resignation of Mr Dyke and chairman Gavyn Davies had been "honourable" they were the right decisions.
"The truth is their position had become untenable. This is a dent in the
family silver, but that does not mean we want to throw the silver away."
Friend of journalists
He said the time was right for a full review of the BBC's editorial system, praising acting chairman Mark Byford as "a fine man who has public service broadcasting running through every vein in his body".
However, former BBC Today programme editor Rod Liddle said Mr Dyke may come to regret his resignation.
He said: "He was wrong to go, the BBC has lost the finest director general it has had for many, many years.
Boris Johnson said Greg Dyke should have "stuck to his guns"
"He was an excellent director general and a friend of the journalists and someone who was committed to public service broadcasting and the independence of the BBC."
John Simpson , the BBC's
World Affairs editor, also paid tribute to Mr Dyke, and to Gavyn Davies.
"Greg Dyke and Gavyn Davies made up unquestionably the most effective
management team at the top of the BBC during my 38 years with the
"They brought a new sense of vigour and success to the way the
BBC was run."
Mark Wood, chief executive of ITN, said Greg Dyke "galvanised and transformed" the BBC.
He said: "In doing so he enriched the entire UK media industry.
"He leaves behind a more dynamic, confident and creative organisation. His resignation looks to have been inevitable in the light of the Hutton report, but his departure is a serious loss to the BBC and, ultimately, to the public."
Conservative MP Boris Johnson, who is editor of The Spectator magazine, agreed.
"I don't think he should have resigned," he said.
"The facts upon which Lord Hutton made his decision have been known by Greg Dyke for months and months and months. There's nothing new in all this.
"If Greg Dyke thinks there is a reason to go now, he should have gone then.
I think he should have stuck to his guns, stuck to his story. They got it right.
Guts and determination BBC, that's what I say."
But media commentator and former editor of The Scotsman newspaper Tim Luckhurst believed Mr Dyke should have offered his resignation sooner.
Rod Liddle said Greg Dyke could regret his decision
"Greg Dyke had no choice but to go but it would have been better to go at the same time as Gavyn Davies and followed this with a whole-hearted and unabashed apology.
"I very much hope the BBC can now move on."
Stuart Purves, former editor in chief of ITN, told Radio 5 Live that it was regime change of a spectacular order.
"Only 24 hours ago we had the then chairman of the BBC raising a whole series of legitimate questions about the Hutton report ...
"Now we have a new acting chairman and a new acting director general - but the most concern I have is that statement that apologises unreservedly for errors."
Leighton Andrews, the BBC's head of public affairs from 1993 to 1996 and now a Labour MP in the Welsh Assembly, also welcomed Mr Dyke's resignation.
"I am a strong supporter of the BBC. I want to see it emerge from its charter review with the licence fee and its independent system of governance intact.
"The BBC's role is even more important in today's hyper-commercial media
world. But the BBC's director general had become an obstacle to charter
"Lord Hutton criticised the BBC's management for its failure properly to
investigate the question of the 6.07am broadcast by Andrew Gilligan. The
director general is the BBC's editor-in-chief. He had failed the test required
in that role.
"His resignation should not be seen as capitulation to criticism of BBC
journalism, but as an acknowledgement of a systemic failure of management."
GMTV presenter John Stapleton, who worked with Mr Dyke at TV-Am, said Mr Dyke was a "very, very close friend" and he was sure it was a sad day for BBC colleagues "who have lost a very good boss".
"Greg Dyke brings a breath of fresh air to any institution he walks into. What you see is what you get with Greg Dyke. There is nothing he loves more than being out on the newsroom floor with the guys talking about the stories," said Mr Stapleton.
"He is completely devoid of any of the pomposity that may have been a characteristic of some of his predecessors."