Yes, it's early. But let's look at the numbers.
They are outscoring opponents by an average of nearly 3 goals per
match. Their nearest competitor (Man U) is doing so by about 1.5 goals
per match, or just a little over half of City's rate.
They've trounced both the second place and fifth place teams on the
road.
They are 5 points ahead in the race.
They are undefeated. Only Newcastle, who have yet to play a top three
club have only beaten teams that are in 14th place or lower currently,
can claim as much.
They've won what would have appeared to be their toughest match going
into the season if you consider that Man U won 18 matches, drew once,
and lost zero times at home last year.
Though they are supposed to be vulnerable in back, they have the
second-most stingy defense in the league and are conceding less than a
goal per match.
They seem deep enough to absorb a normal amount of injuries, and also
have the buying power to reload as needed should somebody crucial go
down between now and the end of the January window.
Probably the best hope for ManU or Chelsea is that a couple of key
players (Silva, Aguero, and/or Hart?) suffer season-ending injuries
shortly after the transfer window shuts.
And yes... It is still early.