The first point on his list is window management. "This is at the top of the list, because it's probably my most frequent frustration; I'm always looking for the right window," Miller writes, "Sure, you might tell me I can use Spaces or command/ctrl+tab or some other wild method of shuffling between my windows, but if tools like that exist to help you shuffle through the clutter, there's probably a deeper problem here."
He proposes taking ideas from the webOS, which uses its innovative card metaphor to make the most out of the multitasking abilities of the platform. He imagines bringing card view to the desktop, controlling them by gestures similar to the webOS.
Basically, the problem of window management being complex is similar to the discussion "automatic or manual transmission". You can pry my manual gearbox from my cold dead hands, as I'd rather slaughter the world's last unicorn than use an automatic one. In the US, automatics are the norm, but at least here in The Netherlands, and from what I've seen the rest of Europe too, manuals carry the preference.
As many men here say, "automatics are for girls". In the end, it comes down to control. I'd rather trade in the convenience of the automatic for the control and flexibility of a manual gearbox, even if that carries some complexity with it. Of course, modern automatics allow you to shift rather well manually too, but those tend to be reserved for more expensive models. It's the same thing with window management: sure, it can be hassle sometimes (although Compiz' Exposé clone combined with four virtual desktops wrapped around the cube is more or less bliss for me), but you get flexibility and control in return.
In my ideal desktop environment, windows would exist in one of three states: normal, iconified on the desktop, or as a card. Normal is just the normal, resizeable window we all know and love. Iconified means that the window exists as a special icon on the desktop, as some older environments (CDE!) allow you to do. When in card mode, an applications shrinks down to about the size of a card in webOS, displaying a cut-down interface mostly resembling what you'd see on a mobile phone. The most important information is shown, and you can interact with it on a basic level.
This of course integrates with the idea I presented earlier where applications could be "moved" seamlessly, preserving state, from one screen (desktop) to another (phone). In such a scenario, moving a normal window from your desktop to your phone would cause said window to morph into the card state seamlessly. Ah, how I love to dream
Miller is also big on this whole touch thing, whereas I personally find it a massive waste of time and energy when it comes to desktop computing. Touch is extremely inefficient on a normal desktop operating system, mostly because it's uncomfortable for your arms. On top of that, desktop operating system simply aren't made with touch in mind, and would require interfaces built from the ground up. Multitouch has its uses (mobile phones, POS, to name a few), but the desktop most certainly isn't one of them.
Miller seems to think that we should be able to interact with our notifications, pretty much the opposite of what Ubuntu is trying to do with making notifications as dumb as possible. Miller wants to be able to, for instance, write a short reply to an email straight from the notification.
For the love of god: no. Please, just - no. Interaction with an application or window should happen within that application or window. I dislike having multiple different locations to interact with the same window - hence my preference for iconification instead of having a taskbar. I just don't understand why functions I perform on a window are also possible on distant buttons at the bottom of my screen.
A window should be an object, whether it's iconified, a card, or in a normal state; all actions you can do should be inherently tied to that object. Environments today treat windows like just one representation of something illusive (a document, an application) - with other (more limited) representations being the launcher or the taskbar entry. I find this wasted space. When you have a cup of coffee, you perform all interactions on that cup, and not on several representations of that cup scattered across your living room. I would like windows/applications to be treated similarly. End mini-rant.
On topic: Growl is a very good example of a decent, unobtrusive, yet useful notification system, and it's a mystery to me why Apple hasn't bought those guys yet.
There are a few other topics Miller discusses, so be sure to give it a read and post your thoughts.