Unblogged
Right from the beginning, there were problems. The gaps between paragraphs were too wide. I didn't even notice on that first post, but with the link-round-up a few days later, the problem was very obvious and distracting. I eventually figured out how to stop this from happening, thanks to advice from a couple of fellow bloggers who know more about HTML than I do. I later went back to that original post and changed the spacing by manually changing the HTML, but doing so on the link round-up would be a bigger job than it's worth.
After I posted that link round-up, the sidebar kept getting pushed down to the bottom of the blog instead of appearing at the side where it should; I eventually fixed this by reducing the size of the picture at the top, but I don't like needing to make pictures smaller. With one post the following week, the same problem occurred, and shrinking the picture did not help -- I eventually fixed it by undoing a change I'd made to the HTML at the end of the post, something that seems wholly irrelevant to the location of the sidebar.
After posting the most recent link round-up two days ago, the sidebar suddenly appeared in some hideous centered format instead of left-justified, and pushed too far over to the right. This happened a few minutes after posting the link round-up. I hadn't touched the theme HTML. I fiddled around with various things, but couldn't fix it. About ten minutes later it went back to normal by itself.
Glitches aside, the new interface is more difficult to use. In the old one, the buttons you click on to perform various operations are labeled with printed words, like this:
In the new interface, these are replaced with icons which have no words on them. You can see what each icon does by hovering the cursor over it, but it's an irritating extra step. I've never understood why icons you have to figure out are widely considered better than printed words you can simply read. The preview button, which is supposed to show you what the post will look like before you actually publish it, doesn't work -- it just shows you the blog as it currently is, not including the unpublished post you're working on. The HTML version of the editing screen appears not in paragraph format, but as an unbroken block of text which is much harder to edit. There's a "format HTML" button, but it breaks out the block of text not by paragraphs, but by wherever there happens to be a space in an HTML tag, making it even more visually confusing. Before publishing a post, I like to test links to make sure they open as the correct page, but in the new interface, right-clicking a link in an unpublished post and opening in a new tab just takes you to a generic Blogger page, not where the link will actually go.
The new interface is better in a couple of ways. When you're editing an existing post, you can save changes without having to close out of the editor screen. The stats display is more logical, though the "traffic sources" information seems to have disappeared.
But overall, the new interface still needs a lot of work before it's even as good as the old one. I don't understand why they did this. There was nothing wrong with the old interface. It reminds me of New Coke.
Since the last link round-up I've gone back to using the old interface. The last dashboard notification I saw no longer contains the note about it being phased out at the end of July. I suspect they've gotten a lot of complaints about this.
I'll say one thing for Blogger -- they do have a history of being responsive when their user base tells them something is a mistake. In 2015 they reversed a potentially-disastrous decision to ban sexually-oriented content -- something Tumblr (or rather Verizon, which owned it at the time) failed to do despite a massive user outcry. I hope that here, too, they'll reverse the decision to phase out the old interface. If it does remain available indefinitely as an alternate option, I'll just keep using it.