It's some of the best writing there is in a comic, web or otherwise, frankly.
Unfortunately, like >>119374648
said, it takes forever to update. Whether due to the artwork being the best around and thus taking forever, or other obligations taking Tracy Butler's time (currently it's the animated short), a page can take months to even a year or longer to materialize. So even with the phenomenal writing, the glacial pace makes it difficult to appreciate without re-reading entire swathes of pages at a time.
That aside, it's also some of the most well researched shit you'll ever find in a comic. Butler goes to agonizing lengths to make the comic period-appropriate, or just to get particular architecture, slang, or a now-discontinued brand of chocolate right, among other things.