Most the voters that gave the Lib Dems 63 and 57 seats respectively in 2005 and 2010 were Labour supporters protesting Blair and the Iraq War and fashioned the Libs as a viable center-left alternative. They were certainly not happy to have in effect voted to put up a Conservative government.
I think the results prove, if nothing else, that people were disgusted with the LibDems with very few exceptions, no matter where their votes were coming from.
What did the LibDems accomplish, except take the edge off some of the Tories worst instincts? The LibDems have been a mopey little caucus that have just propped up the Conservatives as if they were Conservatives themselves. To my knowledge they didn't achieve almost anything they campaigned on; the singular social policy achievement of the government, gay marriage, was spearheaded by Cameron himself. There hasn't really been much of some sort of economic revival that makes the UK stand out from the rest of the world's recovery, and regardless of the nice gesture of the coalition itself, the UK is more divided than it was when the Coalition began, despite the "honorable and steadfast" leadership.
If you support the LibDems you may as well support another party, since they either accomplish nothing or their power gets absorbed into another party in practice. And this is coming from someone who was beating the Nick Clegg drum in 2010 louder than most people, for the reasons Barnes points out.
