re: Just how far are the Pleiades?
Yes, Phil.
I would be a little upset, though, if it turns out Hypparcos had measured parallaxes with a systematic mistake!
For years, I've been telling people the Andromeda Galaxy was not only the furthest thing observed with the naked eye (outside of occasional supernovae) but it was further, much further than first thought.
And it could all be a mistake. Well, I'd have to change the story:)
Raoul