My general advice: the further back you are, the harder you're likely to find the questions - not so much that they are actually harder, but they're more likely to expect different content from the current syllabus. The style has changed over the years as well - you don't get as many idiosyncratic questions these days compared with the early 90s. When you're confident with the questions, this isn't as big a deal, but if you're starting out it can really hinder you. (From your posts, I suspect you wouldn't have a problem personally as you seem to know a lot outside the core syllabus. But if you want other people to be able to contribute, they're more likely to do so for more modern papers).
Continuing along those lines, the 2007 paper is likely to be the closest approximation to what this years' paper will be like. For that reason, a lot of people like to leave it as a "mock" paper to do closer to the time of the June exams.
So my general advice would be: start at 2006, work backwards as time/motivation allows, and then do 2007 close to June.
As far as solution threads go: there are other solutions available for the 2000 and later papers, but I don't think that should stop you. There's also an issue of whether people with have the papers - not as many people seem to have 2004,2005,2006 as the other years.