The first change you will notice when you edit your post. In "Compose" mode, you get a shiny new toolbar - similar to what you'll see in GooglePages. Almost the same buttons, almost in the same order. The two attachment buttons - for Photo and Video - have been combined into one labeled "Image", and moved to the left. Full Justification is gone. And spell check is gone (no major loss there IMHO). But most others are there, and in the same left to right order.
The major change that you will see is in "Edit HTML" mode. The toolbar there is gone.
And it's the same crappy small editing window. The one change that we've been waiting for - still somewhere in the distance.
In Blogger In Draft: New Feature: New Post Editor, we see
... there are a handful of other features from the current post editor that are on our to-do list for the new editor. If you rely on any of these, you may not want to use the new editor for everything just yet.
Yet, there are improvements.
- The well known vertical spacing problem, caused by the "Convert line breaks" setting and use of "Edit HTML" mode, has been eliminated by a more robustly designed post editor, and a new setting which applies in "Edit HTML" mode. The new setting will be found in "Post Options", which makes it settable per post, rather than per blog. Line break sensitive objects in the blog, like lists, preformatted blocks, and scripts, won't be broken any more by extraneous line breaks.
- The ability to display typed HTML, literally, as HTML, without having to labourously convert each "<" and ">" to "<" and ">", before publishing.
- An improved picture insertion procedure, with each picture being inserted where the cursor is, rather than at the top of the post.
For a more comprehensive, and optimistic, evaluation, see Roberto's Testing Blogger-in-Draft: Post Editor - Compose Mode.