A+ for use of 404 profanity Lucy.
I've just spent some time trying to find that JohnMu post in which he said 410 was handled differently. I couldn't find it(which doesn't mean it doesn't exist) and I couldn't find any other Google employee saying that either.
Another aspect of this 301 vs 404 vs 410 that I'm curious about is what happens if I 404 a lot of pages but some months down the road decide to re-use the same url(or do so accidentally) should I expect any ranking problems due to old history?
Google never forgets a url but I might, ya know?