Fairshares Submission to the review is now available online. I include aquote from the review which supports STV.

These direct comparisons of ward and constituency data in the areas of Scotland with the highest proportions of rejected ballot papers in the Scottish Parliament
elections show that these voters found it relatively easy to cast valid STV votes. We would suggest that the percentages of rejected ballot papers in the local government elections
would have been even lower if both sets of elections had been by STV. Had STV been used for both elections, the percentages of rejected ballot papers in the Scottish Parliament
elections would most certainly have been much lower.

Fairshare Submission to Scottish Elections Review (31 July 2007)