(The caveat is that he's still a comparative child of 37, an age by which most people believe they've achieved their emotional and intellectual maturity, but realize they were wrong after achieving real maturity 47. And 57. And 67.
My personal rule of thumb (for which I'm surprised to find actual evidence) is that, when you can choose, surgeons, pilots and most others who take your life in their hands should be in their early 50s -- old enough to have seen every emergency but not old enough for physical ailments to keep them from doing anything about it.)
Schmidt evidently trusts Page to run Google's day-to-day, but isn't ready to go play golf or sip capuccino with Steve Jobs 24-7 just yet.
Which probably means, given that the titles are changing but not the people, that not much will change at Google, at least from the outside.
I could be wrong.
Reaching into ancient history for untenable comparisons about succession, Caligula was trained from a child to take over as emperor from his father Germanicus, one of the most respected, successful emperors and administrators of his era. Despite the training -- far longer than Page has had at Google -- Caligula was...not.