"If you trawl back through those threads from 2011, you can find many of the arguments against AV. As a nation we considered AV, we found it to be imperfect and we decided we preferred our existing, also imperfect, system."
I won't bother trawling through 2011 threads to find arguments against AV because I know them all, or at least most of them, having made them myself at the time (not here, obviously). Since then I have changed my mind. Of course AV was rejected in 2011 -- I'm unconvinced that it was a referendum held in the best circumstances, and as I've hinted earlier at least some false arguments against it were put forward -- as well as the distracting issue of its being a proposal from the Lib Dems, who... well, haven't been popular since joining the Coalition. It is possible and not entirely unreasonable to cast at least part of the rejection of AV as a chance to stick two fingers up to Nick Clegg for breaking their promises.
As best as I can tell now, AV while by no means a perfect system is at least as good as FPTP -- this is true almost by default, because AV reduces to FPTP when there are either only two candidates or when voters decide to express no preferences beyond the first one, as many may well do. Since it contains FPTP within it by definition how can it not be at least as good as that system? And then it's "better" because it allows voters to express more nuanced choices than a single cross.
But if the arguments one way or another have been made here before I'll stop there on that one at least. What bothers me is that people are happy to accept the flaws of FPTP or, sometimes, refuse to even recognise them. And then offer up defences such as its being simple (granted, but then it's also too simple, which is the problem -- it's unable to cope with the more complex politics we have these days), or its delivering strong governments, which while true in general seems to overlook the fact that these strong governments are being delivered based on fewer and fewer votes.
It seems to me that, aside from the more technical problems, there are three basic issues with politics at the moment. Low engagement being the main one, seen not only in lower turnouts (a rise from the historic low of 2001, but still very low), but also in a reduction of support for the two main parties. Again, a trend that seems to have reached for now its low point, but a worrying trend all the same. And then this low engagement with the main players isn't turning into much representation for alternative political movements, the SNP aside. And so the third problem is that the main parties don't even have to care about the first two.
Electoral reform can help to fix this, be it PR, or preferential voting, or just constituencies redrawn in such a way as to increase the number of marginal seats; or the second chamber can be made an elected one also, or local politics could be reformed ...
As long, though, as the answer to the question is "Should the make-up of parliament represent the wishes of as much of the electorate as possible?" be "yes", then the current system is never going to be adequate. How you change it is a matter of what you think the next question should be, but change of one form or another has to follow from a positive answer to that question.
Perhaps, in the end, the real problem for electoral reform in general is that most people just don't care. And that in itself is sad.