I agree 100% with raptor22.
It's a quite clear and well planned test method that McLaren uses. It's a step by step method where you're eliminating as much variables as you can, and concentrating to understand that specific and most important one : tyres.
As for 2010 tyre testings, yes, all teams had tested Pirellis in 2010, but by the first 2011 test, Pirelli changed compounds significantly, using the 2010 data, so the 2010 Pirelli test was more useful for Pirelli than the teams...
Actually McLaren is now the only team with some baseline data regarding 2010 car+new Pirelli compounds. I don't know why is that so hard to understand, that this way they are sure that everything they experience now with new Pirellis, is due to new car's characteristic, and not some unknown reason.
EDIT : Also they would be very stupid if they go for a very high nose, because as many others noticed, they need a lower nose because of the free airflow to the sidepod channels. Even if you look at the upper front suspension arm, even that arm is bent down in the middle ( it's not straigth as on other cars ), to improve airflow to the sidepod channel.