I can't speak for other bloggers, but I personally feel that the level of cross-blog debate has increased (in my experience). Of course that is because I tend to seek out challenges to my views, and avoid echo chambers like the plague. My blog-habits tend towards polymaths like Razib and Steven, moderate liberals like Matthew and Kevin, and civil conservatives like Tacitus and Dan. To be brutally honest I have found more instances of echo-chamber thought on the right than on the left, but that opinion is certainly open to vigorous debate.
I do read partisan sites such as Kos and Atrios avidly however, because in general the media's Establishment bias (not liberal or conservative) requires going to these sources for the missing information. I also read partisan sites such as Glenn and Brian to gauge what the other side is thinking, and have generally found that their accusations of bias are more driven by "doesn't agree with my opinion/interpretation of the facts"-ism rather than "biased intent to actively suppress information"-ism. I've found that right-leaning partisan sites are in general quicker to accuse "the left" and "liberals" of treason/fellow traveling/sedition/etc, because they are unable to grant that the reason there is disagreement is because of interpretation of data and disagreement on certain basic axioms. For example, if you have an a-priori belief that the war on Iraq was relevant to the war on Terror, then anyone who does not support the war on Iraq must harbor secret sympathy for Al-Qaeda. QED. The idea that perhaps those people simply dont accept the initial proposition, and are arguing their case out of the same shared sense of concern for their Nation, is simply dismissed.
In general, it's the right side of the blogsphere that has grown more strident - with notable exceptions - and several conservative free thinkers are beginning to find themselves on the receiving end of the abuse that follows any attempt to stray from the party line (the most notable case being Andrew Sullivan). Not to say such witchhunting doesn't occur in the leftSphere either, but when it does, it is far more a niche phenomenon.
What I want to do is create a kind of forum or public space that exults in the old spirit of debate, the cross-sommunication of ideas, th ehashing out of policy with input from left and right, a true synthesis where people can argue and disagree without the world hanging in the rhetorical balance. But who else would I recruit to join me? I have some ideas, and maybe I'll act on it.