So the latest reveal was a controller as myself and most people had already predicted. The controller itself is well ... odd. They've replaced the standard two analog control stick design with two circular trackpads. It has a touch screen and triggers in the top and in the back of the controller. Due to the size of the track pads the "generic main four buttons (ABXY)" are moved oddly around the touchscreen. This is what I predict will be the major problem of the controller.
First off I have to say I really like the trackpad design. I've played a couple of strategy (EU4,CK2, CIV) and FPS (Serious Sam, Minecraft) games on my laptop trackpad a few times when I left my mouse at home and found it infinitely better than a controller. I personally can't play FPS on a controller at all but with a trackpad I'm surprisely decent.
However, I have a mouse and keyboard for FPS/strat and I don't ever see a time when I would be without either a mouse or trackpad so I don't see why I would need a controller designed around playing these genres better. What I use a controller for is platforms, fighters and aRPGs where button mashing and precision analog control is the primary need. My concerns with the way the generic main four buttons are pushed into what seems like a fairly awkward spot would harm the genres which controllers perform the best on.
I can understand that they were trying to develop a controller that would be useful for lots of genres while being slumped in front of the couch but I still think a wireless keyboard and a mouse on a lapdesk is the better alternative. You have the benefit of mouse aiming but also being able to use other computer functions like web browsing with ease. I suppose the touchpad (assumed it emulates a keyboard) will make typing easier so it might not be a massive trade off after all.
The controller is software moddable which is always nice but it doesn't seem to have the modular design Valve originally patented that would allow components (like a single trackpad) to be traded out for another. Perhaps this is coming in the future but it seems odd that they didn't outright say that it will be modular with optional components.
Now what will really make or break the controller is how much it costs. Two trackpads and a touchscreen sounds extremely expensive to me. I don't think people will consider putting serious cash into a controller no matter the tech it has when you can just get a Xbox 360 controller off ebay for $15.