Just wanted to say that I have been watching this and testing caffeine since the anouncement months back. At this point I can say with some confidense that what I saw prior to a few weeks back was indeed caffeine results in the normal search. It appears since shortly after the beggining of November Google pulled Caffeine back and is testing it randomly on a few data centers. So I agree with the conclusion that Caffeine was implemented and being served for well over a month. Just wanted to give my 2 cents. Currently I am seeing caffeine randomly after reloading a few times on http://209.85.225.103/search?hl=en&q=widget&btnG=Search&aq=f&oq= Try it for yourself
I just tried that search and get the same as I get on regular Google. The caffeine DC is much different.