Last year I thought the most significant change was Red Bull's pull rod rear. The car seemed to be able to respond to any circuit design and only struggled when their engine couldn't keep up.
They also have a very short wheel base which seemed to make the car very nimble in the corners.
The Mclaren this year has moved to the pull rod rear which I was happy to see. I'm still concerned about the long wheelbase approach. The car seemed downright clumsy in the slow corners last year. What other than straight line and high speed cornering stability is the advantage of the long wheelbase? These are important factors, but that hasn't been where they gave up huge performance deficits last year.
I love the fact that Mclaren is always searching for that "eureka" moment. It fits with their leading edge technology philosophy.
Let the show begin!