First off, denise and sarah, congratulation on your purchase of Wedded Bliss level 1 (Civil Edition). I wish you many more leveling together, and blissful hours of play.

Feedback on the mockup:
fu did an amazing job with that! I love the right sidebar with the passion of a thousand thunderstorms**. I've been longing for some usage of the blank space there for ages.

The collapsing boxes is a neat touch, even though I'd be pretty much okay if they weren't. The improved tag autocomplete is A-EFFIN'-MAZING (despite the few bugs, but judging by the comments, fu's already on the fixing it part :D). At first glance the tag box seemed how so tiny, especially compared to the long boxe currently in use, BUT it is auto-expanding! ♥ fu, again, AWESOME!! The tags placement doesn't bother me, but I suppose it's because I always thought of it as being part of the {currents|metadata} section of an entry. But I wouldn't be bothered if the box made a return to its old place in the next mockup. (Something most of the commenters seem to be asking for.)

The various see bigger popup are nice too, though, except for the custom mood and icon selector popups, I don't expect to use them.

Other thing of goodness: The scheduled/draft options are logically placed within the date/time section. I particularly like the separation of 'use publishing time | use custom time' (with 'date out of order' option, though it's not called that) from the 'publish now | publish in the future' options. And there is a popup date picker! Thunderstorm levels of loves people! The draft/scheduled/ posts listing is a bit confusing, it lacks a clear demarcation between scheduled and draft/unpublished sections.

I was a bit thrown by the publishing section being below the post at first. I was expecting them to be in the sidebar to be honest, but having it down there makes sense as well. I don't know, I'm not sold on either placement to be honest, it was just a weird 'but where are those options?' moment. hope has a very interesting feedback, with a mockup proposition I rather like.

As far as the keystroke navigation goes, outside of checkboxes not checking when in focus and the enter key is pressed, I have to say, it's a real improvement! I really like the ability to (un)collapse sidebar boxes by taping the enter key when the title has the focus.

Overall, the mockup is really, really awesome. That a thousand thunderstorms of YES, THIS! from me. Give or take a few adjustments to make it even more rockin'. I have no favourite parts, because all are equally awesome in their own right. (The unpublish feature is one I never dreamed of, but now I want it yesterday :P)

ETA:
- The icon box looks big, which may be due to the precedent place it had. I think the fact that the some of the posting options were on its left made it seem to take less space.
- I love the tiny icon when the icon box is collapsed idea mentioned way earlier in the comments

(Technical PS: I've taken the demo for a spin with Ubuntu 10.4 laptop & Firefox 3.6.3 and javascript active.)