Button is wary of Mercedes GP for 2012
Jenson Button thinks that caution will be needed with the Mercedes team in 2012 because the team led by Ross Brawn has been working on their car for many months.

Jenson Button won the Formula 1 World Championship title in 2009 with the Brawn GP team, which has since become Mercedes GP. The Briton had an ingeniously designed car that had been developed very early, and he believes it could be the same for Nico Rosberg and Michael Schumacher next season.
Usually, there are three very good teams in front, with Red Bull, Ferrari, and us (McLaren). But we have to watch out for Mercedes. They’ve been preparing for 2012 since mid-season – just like they did when I became world champion, Button told the German news agency SID.
The German team has recruited some very good engineers this season, including Bob Bell, Aldo Costa, and Geoff Willis. These three men have all collaborated on the design of the MGP W03 for 2012, and it is this technical reinforcement that has led to the extension of Nico Rosberg’s contract, who hopes to secure the first victory of his career in 2012.
The determining factor for Mercedes in 2012 could be continuity, as few people have left the team and new ones have arrived. Moreover, Nico Rosberg and Michael Schumacher will be starting their third season with the team, and therefore they know its operations well, which could be an advantage if they also have a good car.