Deal done and it's a "win, win" for everyone: customers, staff and shareholders. That was the message both companies presented at the press conference in Paris I've just attended.
PSA sounded delighted to be buying. The Chairman of the board, Carlos told journalists he's excited about "unleashing the potential" of Vauxhall Opel, a company which has lost money for the last 17 years.
GM sounded delighted to be selling. The company retains the pension liabilities and takes a massive write-down on up to 4.5 billion Euros - some will see these as evidence of a strong desire to offload.
The logic is that combining forces there's money to be made, and savings to be had. PSA has identified 1.7 billion of "annual synergies", in "purchasing, manufacturing and R&D" but won't say more. There will be losers as well as winners, we just don't know who they are yet.
The union is concerned about the future of the Vauxhall plants at Luton and Ellesmere Port and the 4500 people who work there.
PSA says Vauxhall Opel will be making money again by 2020. Can this be achieved without factory closures? "We do not need to shut down plants," Tavares said "as long as performance improves".
Tavares repeated a pledge to honour existing contracts - reassuring but also unsurprising, to have broken one would have risked a legal challenge - but he danced around invitations to commit to the factories on a long-term basis:
Can PSA guarantee it will always build cars in Britain? "What we can commit on is that we are going to bring to our UK friends the best of experiences".
Does the uncertainty thrown up by Brexit mean the risk a British factory will close is greater? "Being a hard Brexit or a soft Brexit you and me we do not know, so the only thing we know is that we will have to adapt".
ITV News Business Editor Joel Hills reports from Paris
Would a hard Brexit make Britain less competitive, less efficient? "It's not for me to answer that question".
The prospect of Brexit has already had an impact on Vauxhall/Opels fortunes. GM Europe lost money last year because the pound fell in value -much of the company's revenues are in sterling, its costs fixed in Euros.
Ellesmere Port looks particularly exposed. The workforce there is efficient but the way the Astra is assembled there is not. 75% of the parts used to make the car are not British they are imported. Most of finished cars are exported again, most of those to the EU.
The GM supply chain is entwined, stretches across a single market and a customs union we look set to leave. Tariffs, quotas, any restrictions on the free movement of components across borders would make the case for PSA building cars in Britain weaker.