I've only been using the new site for a couple of hours, but here are some initial thoughts:
Navigation: When I click through a post within a category, how do I quickly get back to the category and the particular location within the category feed? For example, let’s say I’m browsing posts in the “Bugs & Features” category, and I click into an older post page. If I click “Community” on the top banner, I go back to the main feed, and if I click “back” on my browser, I end up at the top of the category feed. That’s a bit cumbersome if the post of interest was ¾ of the way down the feed.
Scrolling: As others have mentioned, a lot of scrolling is required with the current set-up. I’d like to see less information (and no avatar) for the posts on the feed pages.
“more”: Once I click on “more” to expand a post from the feed page, it would be helpful to have a “less” option as well to collapse the post, which would further aid in navigating the feed page.
Containers: I agree with what Manfred mentioned below regarding container size – widening the center container would significantly improve the experience.