First of all, I love the expansion of the components, Data, and Events over all the versions I have seen.
It is great to be able to get an app 90% done within Designer.

That said, I think the additional features for the UI (Categories and Toolbar) are a little annoying.
I like to have the screen space to expand the Inspector and still see the full app (ex: iPad).
Maybe if these features were collapsible so you could hide just the categories and toolbar, but leave the Toolbox open with the current category list?

How about a slimmer Toolbox with Categories in a drop down (select field) under the Filters (i love the filters too, by the way!)

The Toolbar (with the ginormous icons) could just go away IMHO.

Under Actions you could have an on/off switch for both Toolbox Categories and Toolbar.

Last, but not least...
I would like to be able to drag from toolbox to Inspector while in code view, I have run into this a few times while setting up stores, fields, and such.

Hope this is helpful, thanks.