Feedback on new editor layout

Not as bad as I initially thought, although I don't think you should say it functions like the default MediaWiki editor until you fix a few things:
#The preview and show changes buttons. Part of the reason why people use the default MediaWiki editor is that they don't like the lightboxes that are used everywhere - and the ajax preview doesn't have the advantage of leaving a mark on your history, which is quite helpful if you want to go back to your version of the page as it was when you last previewed it. Furthermore, you can't close the ajax preview while it's loading, and it fails to preview the page.
#Load speed. This new editor takes considerably more time to load up than the default MediaWiki editor. There must be a few things loading up that aren't necessary - I'd suggest taking out the sidebar; people who use the default editor aren't likely to use those buttons, and removing the code necessary to have those will certainly shrink a file or two.
#Heavy JS dependency. Assuming phones aren't specifically accounted for with this new editor, you can say goodbye to editing on a phone without an app - the new editor takes quite some time to load on a computer, I have serious doubts that it'll be able to load on a phone. Not to mention that if you're editing from somewhere JS is blocked, you won't be able to edit at all - whereas the default MediaWiki editor would be just fine on a phone, or somewhere JS is blocked.
#Scrollability. The new editor doesn't scroll - this makes it nearly impossible to put a notice above the edit window. Take, for example, [[Special:Upload]] on Community Central. That notice, were it over an edit window, would be obscured and would entirely lose its purpose - it wouldn't "STOP!" editors and make them read what the template said before they actually edited. Not to mention, allowing the page to scroll gives more editing room, which is always appreciated. On low resolution, the edit window is almost unusable - See [http://img232.imageshack.us/img232/3897/faileditorformoncho.png here] for the new editor at 600x480 resolution, and [http://img24.imageshack.us/img24/5724/faileditorformoncho2.png here] for the default MediaWiki editor at the same resolution. The default MediaWiki editor has twice the editing space - a major advantage over the new one.
Wikia's ToU uses a very strict definition of the word "function" - I think it sends the wrong message when you say that the functionality of this new editor hasn't been changed, but changing the upload button (on the old RTE) to Special:Upload is changing the functionality of the button.

Alternatively, you could fix all of these by just leaving the default MediaWiki editor the same way as it is - I'm sure that's not too difficult to do, considering that all you'd be doing is replacing the RTE with this new one in your code, as opposed to rewriting the entire way <code>action=edit</code> is served to the user.