GiddyPickle and I have argued on several threads about whether you can vote tactically with AV.
The bottom line is that - yes you can - but only if you already know what everyone else is going to do. Otherwise the best option is to vote in order of preference - i.e. not tactically. The fact that in Oz parties distribute "how to vote" cards is irrelevant.
This is the most useful link:
blogs.lse.ac.uk/politicsandpolicy/2010/09/02/tactical-voting-isn%E2%80%99t-a-practical-strategy-in-alternative-vote-elections/
More interestingly:
I think it is true that noone really knows what the effect will be short term or long term. This is largely because people have to vote tactically at the moment and so it is unclear what will happen if they don't have to. It is certainly true that the change in hue of the LDs means that at the next election it is the right wing vote that will be split, so labour will probably lose out under AV. In the past - including the most recent general election - it was the left wing vote that was split.
Cable is trying to appeal to labour voters who are the ones who will make the decision on AV.
Having started out feeling like voting NO in the hope of Clegg getting sacked by the LDs and the coalition falling apart I have decided to vote YES as it is clearly the fairest way to elect a constituency MP. It is not PR - PR is incompatible with constituency MPs.
One big worry for people is that they don't like the current coalition's approach which is to throw away all manifesto pledges and make it up in back rooms. And that AV might increase the likelihood of coalitions as it decreases slightly the under representation of smaller parties.
I genuinely believe that coalition governments could be a good thing even though this one is not. This is why:
Since Thatcher governments have moved more and more to whipping MPs, making cabinet decisions in private and forcing them through parliament etc etc. I would MUCH prefer to see a parliament where the issues were actually discussed, MPs voted more on principle or (shock horror) in the interests of their constituents rather than because the party whips told them to (and bye bye government jobs if you rebel).
A coalition government clearly needs to have some 'coalition agreement' - enough to get a budget and at least some manifesto commitments of the biggest party through. But the detail and other issues would be better discussed in parliament, and we would end up with much better legislation if the biggest party had to publicly convince their coalition partners to vote with them.
This is Clegg's biggest mistake. He could have worked with the tories without having to take 'collective responsibility' for every cabinet decision.