Probably very very few were bought in 2007, but the fact is that they're used in 2007 - and that's what matters.
It's reliable in as far as all the results are completely honest of those who submitted. Also, as I said before, these are people who play games and so are likely to have above average PCs, so I would have thought that don't play games would actually have lower specs than those listed.
When I say 'welcome to 2007' I meant computers that are bought in 2007, which is what Vista is aimed at. Vista isn't aimed at 5-6 year old computers. Technology moves on, so should people, and stop complaining about requirements.