I'm a little dubious over the laptimes posted by McLaren.
At least with RBR and Ferrari, in pre-season testing, they were consistently quick, over many sessions, with various tyres/fuel loads. Moreover, various F1 commentators/drivers all suggested that they are the teams to beat.
With McLaren, they have had 1 good session - a session that I strongly suspect Ferrari/RBR did not go all out to dominate.
Within 24 hours we should all know where the teams truly stand.
What I can say is that McLaren have definitely made a step forward. They've tried out a new (simple) exhaust system which has worked straight out of the box. Originally, I suspected that may be struggling to be the 5th best team, but now it looks like they could well be alongside Mercedes.
At this point, I believe the pecking order to be:
Ferrari/RBR
McLaren/Merc.