A fucking Tory was getting into number 10 anyway, owing to the fact that a coalition with Labour was unworkable (and unsustainable) and if the Lib Dems didn't actively support the Conservatives, they'd be forming a minority government now, and when the inevitable happened and another election was called, there's every chance they'd have ended up with a majority - largely through cannibalising the Lib Dem vote.
A strong Lib Dem coalition with the Conservatives allows them to temper the more ridiculous Tory policies - you can see a whole host of the ones they've already dropped in the news today. It also allows them to get Lib Dem policies in place, and likewise you can see a number of those in the news today. No increase in the inheritance tax level? A fully elected House of Lords with a true PR system? How the hell is that a bad thing?
It's also the only situation short of a Labour-Conservative coalition that gives a stable government at a time when having a stable government is probably the single most important thing we need. There are a whole load of tough and unpopular changes that need to be pushed through right now as a result of the state the country (and the world) is in, and though the Tories wouldn't be my first (or second) choice of parties to do it, I'd rather have them doing it than nobody.
A minority government would be a disaster for the country right now IMO, given how difficult the cuts we need to make are going to be. Both the Conservatives and the Lib Dems are taking hits politically by agreeing to things that a lot of their supporters may not like in order to get a stable government in place. Obviously they're gambling on being able to sort things out quickly enough that the electorate can see what they've accomplished when it comes to go to the polls in five years...