Hilton announced last Friday that he was taking a year of unpaid leave to move to California, claiming he will return before the next election.
The move was widely reported as a blow to Prime Minister David Cameron, as Hilton is the fourth member of his inner circle to have left in less than a year.
But while Hilton's brilliance at pushing the envelope in both policy and messaging has been cited, it has also been suggested that 'not that many people in government will miss him'.
One Whitehall insider told PRWeek: 'Hilton was there to think the unthinkable and most of the time it was undo-able. For every 19 ideas that were undeliverable, there would be one gem that had potential.'
Weber Shandwick chairman of corporate comms and public affairs Jon McLeod added that there may have been 'frustration over Hilton's inability to punch through to policy at a Whitehall level'.
The question now arises of how the Tories will fare without the overarching strategic insight brought by Hilton.
Cameron's messaging expertise is being led by comms director Craig Oliver, whose main contribution has been to gain Cameron better coverage on the crucial six and ten o'clock television news bulletins.
But insiders have suggested that the next phase of the Tories' comms strategy will need to focus on the basic delivery of plans, a world away from the grand schemes characterised by Hilton's Big Society campaign.
McLeod said that Hilton's moment had 'completely passed'.
'Between now and 2015, I believe we will see a move to an even more pragmatic form of government than we have seen before, combined with dog-whistle politics over messages about Europe, immigration and tax. Keep it simple is all it needs to do.'
However, one former Downing Street aide said the Government's priority would be to develop a believable statement on growth: 'There would have been a lot of public sector reform, so the question will come: Are we doing everything we can to unlock growth?'
12 Number of months Hilton will spend on sabbatical in California
17 Number of special advisers Cameron now has after Hilton's departure*
78 Number of special advisers across government*
£5.9m Estimated pay bill for 2011-12 for all government special advisers*
How I see it
George Pascoe-Watson, Partner, Portland
David Cameron will miss Steve Hilton enormously. His drive, energy and refusal to take 'no' for an answer have been powerful attributes. But Government is now in a delivery phase. There are a number of first-class brains in Downing Street.
Darren Murphy, Chief executive, Centreground Political Comms
The Government said it was not cutting health budgets, but then it said that unless it made changes the NHS will run out of cash. One would be hard pushed to say what the point is of public service reform under the Conservatives. Under Tony Blair it was about choice - what is it going to be for Cameron?
Michael Gove among those touted as Hilton's replacement
A number of David Cameron's closest confidants have been mooted to replace Steve Hilton as Downing Street's strategic force.
One Whitehall insider has suggested that potential candidates to take on Cameron's director of strategy role could include Education Secretary Michael Gove, head of policy development Paul Kirby or senior policy adviser Rohan Silva.
None has the marcoms background of Hilton, although as a former journalist it has been suggested that Gove would be able to bring an understanding of media handling to the role.
Hilton's exit follows that of Andy Coulson, who quit during the phone hacking revelations; Tim Chatwin, the former head of strategic comms, who joined Google; and James O'Shaughnessy, who moved to lobbying firm Portland.
Fleishman-Hillard head of public affairs Nick Williams advised Cameron to 'learn from Tony Blair's days and ensure he is surrounded by some big hitters'.
Williams said: 'Cameron needs to spend time rebuilding his team.
'If he does not, then civil servants will step in and his ability to develop new and creative ideas will be constrained significantly.'