While I understand where you're coming from, I feel his criticism is well founded. There is noticeably less contrast and delineation. It also does take more to discover the interface - you have to actually hover over buttons. While you could argue that one would learn the buttons in time, the delineation issue won't go away. There's a reason they put a thin line around posts in G+
The discoverability of the interface is always a trade-off. They probably have enough data to assume that users will in fact learn this interface from daily use. I preferred text too.
Delineation and white space are two related but different concepts. One is talking about some way of separating different parts of an interface, through lines or contrast (i.e. different colors). The other is talking about avoiding clutter, avoiding related items from stepping on each other. In a way, white space should be used for closely related elements, while delineation (there may be a better term for this) to allow you to separate larger items. If you look at the page you linked, the yellow/white contrast clearly delineates where the content column starts/ends.
The end goal is to convey the separation - that is achieved by both. The whole point of the article is that whitespace can be a (more) effective separator.
just noticed they haven't rolled out these changes to everyone, I still have an outline and text buttons: http://cl.ly/2X1r2G322r241K3M2Z0U
People should also note that the "classic" theme is still available. I like the "dense" version of the new theme, though I don't use the web interface much anymore.
Yes, convey separation, but after a certain number of pixels white space is not as effective anymore. Notice how in the example of the table he argues that for wider tables using white space is not effective, and that delineation using colors should be applied.
The brain has to look at a layout and make sense out of it. In real life we're aided by contrast to make sense where one object starts and where the other begins -- without contrast you end up with camouflage. When using white space our brains figure out the delineation based on positioning. If blocks of text are perfectly aligned we fill out the delineation automatically; so lines are not necessary. This process breaks down over large areas since our field of vision is small and we would have to scan the whole area before we would make sense of it.
In the new Gmail layout, the menu items are aligned to the left, and so is the content. There are no "lines" between the menu and content the brain can fill out. Of course we can tell where one stops and the other starts, but it takes longer, it wastes more brain cycles than necessary.
Based on the screenshot we do no see the same version. In your version you have a separation between the menu area and the body of the email, the buttons have text and not icons, so we're not arguing over the same layout. Also, I do not see a classic theme being available.
EDIT: I don't see a classic theme that would look like your screenshot.
since when is whitespace not delineation? the fact that there isn't a 1px border there is irrelevant - the content and the navigation in the space indicated are separated by the largest portion of whitespace on the whole page.
It's not the white space that makes the delineation, is the alignment of the items around that white space. If I plot a bunch of blocks of text on a white canvas you couldn't make columns or rows out of that mess. You'd have plenty of white space, but no delineation.
A bigger problem for me is not the visual separation, but that there are functional, but invisible, frames in the layout. The header doesn't scroll, while the left sidebar and the main content scroll separately. So, in the middle of the whitespace there's a place where scrolling changes from scrolling the left panel, to scrolling the main content.
Without the line delineation, I found myself with the mouse hovered over the left column trying to move the main content and wondering why my scroll wasn't working. If you have tall enough content in the left sidebar a (non-standard) scrollbar appears (sometimes). But if you don't have content there, or aren't moused-over the correct areas, you don't get any indication of what's happening.
If the page was a normally scrolling page with no frames, the whitespace is not terrible to me. The way the page functions, it needs the 1px frame that Google+ has.
This is even a bigger problem on small screens. On my 13" laptop I can barely see 2 contacts in the chat list and have to move my mouse over it all the time so that it grows to 5 contacts and try to scroll those.
I laughed when I saw the massive arrow pointing to the large object that delineates the exact shape of the thing that isn't delineating anything apparently. A perfect instance of not being able to see the wood for the trees.
