A discussion by the Political Studies Association with no party bias on AV looks at all the points on both sides (thanks Nwhyte and Communicator)

It's very even and I found it an interesting read.

It also cleared up a point that I'd been misled on.  If you want to vote in the traditional FPTP in an AV world, you can just list your first preference on the ballot paper and leave it at that.  You don't have to list further preferences unless you want to.  (In Australia, I believe you have to list them all in order, but that's not the way the UK will be doing it)

I'll be voting for AV, though the study makes it clear that AV is not actually going to make any dramatic changes to our political landscape.