Thanks to Scott from Banana Stew for laying out the new beta feed URL's in a comment here. This belongs front & center... The url's are laid out as follows:

The URL for the post feed is:

http://beta.blogger.com/feeds/blogID#/posts/full

The URL of the comment feed is:

http://beta.blogger.com/feeds/blogID#/comments/full

The URL of the per-post comment feed is:

http://beta.blogger.com/feeds/blogID#/postID#/comments/full

• The URL for the short form of each feed is at the same URL, but ends with /summary rather than /full.
• I would imagine that these feeds can still be run through Feedburner to gather & report accurate subscriber stats.
• To access these feeds in RSS 2.0 rather than Atom 1.0 format, append &alt=rss to the end of the URL, as described in Blogger Help.
• To find out your blogID, sign in to Blogger beta, then head to new post, or to manage posts, settings, or layout. In each case the end of the destination page URL will be your blog ID.
• To find out a post ID, head to a Beta post page, & select the "post a comment" link. The end of the "post a comment" URL is the post ID.

As discussed in the comments at The Last Word, the link to the whole blog comment feed seems to be awol for a significant number of users (me, Ramani, & Adi, at least), but the URL above holds up, & let me make a sidebar widget....

With this info in hand, I've road-tested Ramani's "recent comments in the sidebar" method on FreshblogBeta. To get this to work, log in to beta and select "layouts." Add a sidebar page element, & select "feed" from the list of options. Enter the feed URL (your beta blog's comment URL, for example) in the pop-up window, and an options window will appear.

This will give you the opportunity to change the title of the sidebar box, as well as to add dates & authors to the content titles. This means that you can add summaries of recent posts on related blogs, (as well as a quick & easy recent comments section) to your sidebar. Excellent.

One other feed-related issue. As Philipp points out in the update to his announcement, having the new feeds be beta URL's could later present a problem after everyone has migrated and the system isn't in beta anymore.

While we're walking through the beta, here's a round-up of recent discussion:

• Improbulus explores the detection of labels as tags by Technorati & not by Icerocket
  
• Julie walks through the current state of play for anyone who has the option to migrate & isn't sure whether to make the move. The comments on Julie's post also point up an anonymity issue. If your GMail account has your real (and / or whole) name, & your anonymity is valuable to you as a blogger, don't use that account to migrate with.
  
• Imp (again) has the scoop on updating your tagger userscripts so that they'll work in the beta. This fix points scripts to the new beta pages, and will work as long as the underlying functions are still possible, & only the locations of the pages that you want to modify have changed.
  
• Peter @ Blogger Tips & Tricks walks through the greatly simplified process of adding advertisements and affiliate content to your beta blog using layouts, which seems to have been a significant target of the upgrade.

Nice to breathe out, relax, & start to see the lay of the new beta land a little.

Filed in: google blogger blogtech webtech beta

See also:

• Get Blogger Beta Labels without Layouts!
• Blogger Beta for the Weekend
• Blogger Beta Update, Incl. Template News
• Beta Comment Notifications
• Beta Templates, Layouts, & Tags
• Under The Hood: Blogger's New Labels
• Blogger Beta Explored
• Significant Blogger Upgrade