Take for example its coverage of the torture/Guantanomo issue vs. that of the war on Iraq. It opposes the Republicans on the first, the anti-war Dems on the second. However, criticisms of the torture policy are always just that, criticisms of anti-war Dems are always the occasion for snide 'analyses' of the weak on foreign policy (in their view) Democrat Party. A decade ago they strongly supported the forcing out of Clinton from office over perjury in a civil case unrelated to his actions as president.('Just Go' was the cover story). It would be utterly inconceivable for them to do the same to Bush over torture, the NSA scandal or, I suspect, any other gross violation of the law by the Republican president as president.
There still is interesting stuff, but much less than before. It's too bad, it was a great paper.
One interesting thing I would note is that there coverage of Bush's policies in the Middle East and in Iraq specifically have become subtly more critical during the last year. I could be wrong, because I don't subscribe to the magazine and only read it on occasion (although I probably at least look at most issues on the newstand): still, I think they are less impressed with Bush's foreign policy than they were. Still, in terms of domestic US politics, there bias is obvious. I'd also say that they have a strong bias against the Liberal Democratic Party in Britain. Bagehot and Lexington are probably the two worst parts of the magazine.