While I'm at it...
Generally speaking, I'm rather impressed with the system used for elections to the Scottish parliament - a number of constituency MSPs elected via First Past the Post, followed by a further number elected via lists to top it up, on a proportional basis.
However, there is one very significant weakness to the system: if a particular individual gets themselves into a position at the top of one of the 'big' party lists (SNP, Tory, Labour), they're pretty much guaranteed a seat, and it becomes effectively impossible to get rid of them. That's really not democratic - the electorate really should have a meaningful ability to elect or reject a candidate.
(There's a case in point here: one of the Tory MSPs has been in the parliament on the list for 17 years. In that time, he has stood for a constituency several times, and been unsuccessful every time. And yet, despite that explicit rejection by the voters, he remains in place.)
I'm inclined to think that this quirk of the system should be closed, if it is practical to do so. And, fortunately, there's an easy fix: institute a one-term limit for MSPs serving on the list.
That is, if an MSP enters the parliament by winning a constituency, they should be free to stand for re-election and continue in their role. If, however, they enter parliament by virtue of their position on the regional list, they then become ineligible for a place on a regional list at the next election. If they want to continue in the parliament, then they must fight a constituency and allow the electorate a say on them specifically.
(This doesn't entirely eliminate the possibility of a party playing the system. But it's enough of an improvement that I think it's worth doing.)
(I should note that this also hits the Green party harder than any other - since they don't have any constituency MSPs, all of their incumbents would become ineligible for a second term (unless they did happen to win a constituency). Even then, I'm not convinced that that's too terrible, as the main effect would be to expand their range of people with parliamentary expertise. Which is surely no bad thing?)