Dr John Reid's departure was greeted with derision by Sinn Féin and the DUP, although neither chose to criticise him on a personal level.
Mr Gerry Adams said the outgoing minister's record was one of "dismal failure" while Mr Ian Paisley jnr said it was a case of "bye-bye John, bye-bye Belfast Agreement".
The Sinn Féin president said Dr Reid had "failed to grasp the imperative" regarding implementation of the agreement, adding that he did not wish to see any British secretary of state in Belfast and urging the incoming man to end suspension of Stormont and to call all-party talks.
Mr Paisley jnr said it was clear to him that direct rule was being entrenched and he expressed the hope that renegotiation of the agreement was possible. Other anti-agreement unionists accused Dr Reid of talking tough but ultimately failing to deliver.
Mr David Burnside, the UUP MP for South Antrim, said: "At no time did he apply the full force of the state against the paramilitaries and I think the republican movement walked around him."
The pro-agreement section of the Ulster Unionists spoke in more muted tones.
Mr David Trimble appeared to link Dr Reid's departure with what he called "revelations about recent events in the Northern Ireland Office and at Stormont" - a reference to the alleged republican spy-ring operating at Parliament Buildings and Castle Buildings.
He was known to have been critical of Mr Reid's decision not to inform him, as First Minister, of details of the spying allegations before the controversy broke.
The UUP president, Mr Martin Smyth, said "unionists will be shedding no tears with his departure", he said.
Sir Reg Empey thought the move to London was a "convenient break" for Dr Reid, who had suffered some bad political luck.
"It hasn't worked out terribly well for him because we are in a position where the institutions are suspended," said the former industry minister.
Both the Women's Coalition and the Alliance Party voiced concern at the switch in personnel at a time of suspension.
Mr Mark Durkan, the SDLP leader, also voiced some criticism. He accused the outgoing secretary of state of being a better talker than a listener and of appearing to relish the return of direct rule and the greater powers that came with it.
"However, in the last two years he did make a positive contribution in the development of the peace process," he said.
On a more positive note, the Minister for Foreign Affairs, Mr Cowen, congratulated Dr Reid on his new appointment and expressed "personal regret that John will be relinquishing his portfolio".
He added: "John has applied his considerable political talents, his formidable intellect and his enviable communications skills to significantly advancing the peace process."
There were also tributes from the Tánaiste, Ms Harney; the Green Party leader, Mr Trevor Sargent; and the Fine Gael leader, Mr Enda Kenny.