A long time ago (so long, it would seem, that references are currently un-Googleable), there was a folk consensus that examples of products manufactured on Mondays and Fridays were to be avoided and that quality went up through the week and peaked at Thursday. I'm not certain if anyone ever proposed a specific time of day on Thursday where the smart money might be placed. I'm thinking I have had the good fortune to have an early Thursday model and you had the very great misfortune to have had to deal with both an early Monday and late Friday sample. This would seem to be well outside of likelihood.
Seriously, had I had your experience, most probably I would have ponied up for the D800, too.