Andrew Rawnsley. Tells it like it is.
Yes, I'm a big fan of AR, too; he offers really good insights from first-hand sources in government, and writes really well. I also like his Observer colleague (and economics commentator), Will Hutton (among other things, he was warning about an inevitable global financial crash and banking crisis years before it finally happened in 2008, but as usual, no-one took any notice until it was too late).