A couple of days ago, AOSP was graced with a series of freshly created "l-preview" branches and a massive push of brand new code. As we know now, quite a bit of that code push wasn't truly representative of the L developer preview. (Very sneaky, Google.) Most of the truly new updates belonged to GPL-licensed projects, which Google is obligated to release in a timely fashion. The remaining projects with "l-preview" branches were filled with a recent snapshot from the Master branch.
While we didn't get enough code to build our own versions of L, there is still an obscene amount to look at. Since it's not a sign of good mental health to obsessively crawl around each project looking for changes, we usually wait for Al Sutton of Funky Android to generate a full list of commits with developer comments.
This time, the full changelog comes in at a whopping 60,305 commits. Even if we drop everything from the Chromium project, that number only drops to 36,637. Unfortunately, this list might contain some changes that never made it into the L factory images, and it's obviously missing a substantial number of the most important updates.
Fun fact: Despite being a partial code dump which lacks most of the major platform changes, L already has 3,500 more code commits than the update from Jelly Bean 4.3 to KitKat (JSS15J 4.3_r2.1 to KRT16M 4.4_r1).
If you're up to the challenge of looking through all of these developer comments, head over to Funky Android and check out this monster of a changelog. The full changelog, with Chrome commits included, weighs in at a hefty 10 MB. Some people have even complained that this page can cause Firefox (and possibly other browsers) to crash or freeze up. You've been warned.