Matt, along with folks like Brian McFadden, Jen Sorensen, Ted Rall, Ruben Bolling, and Tom Tomorrow, have made huge inroads over the years towards the mainstream acceptance of "alternative" style cartooning as a voice in journalism. Substantive questions, criticism, and satire are woefully absent in most of the media's output these days, and it's been a huge relief to see that vacuum filled with progressive cartoonists.
Rather than focusing on hackneyed visual metaphors and topical mash-ups found in the editorial cartoons of yore, it seems editorial cartooning has (thankfully) started to shift towards ideas that have as much depth, breadth, and thought as any 1,000 word editorial. All this has occurred while TV news is moving in the opposite direction, trading journalistic integrity with corporate profit, sensationalism, mediocrity, and pundit-culture.
Matt's work can be found here. Also, for those that missed it, here is Matt discussing his work while visiting Chicago in May of 2011: