The problem with the XBO is that MS is going to attempt to unify the OS too much to get parity with Windows Phone and Windows 8. I understand their desire to do so and don't really fault them for it, but a device is a device and there are different purposes for the devices. I do not have the same needs from a gaming console that I have for my touch screen phone or tablet. We've already seen what the philosophy has done to the desktop, which despite my love for tablets, is not going to die.
A console interface should not be setup around a touch screen backbone. We are not going to be accessing anything via a touch screen interface, at least not primarily.
XBO UI does a lot of things right, but the core is wrong.
Sony's XMB and PDM (wish they'd just kept the XMB title) may not appear as flashy or as cool, but it's core simplicity keeps the functional purpose of a user interface intact. That purpose is to be a system by which the user interfaces with the device. Efficiency and accessibility should always trump flashiness.
Apple has been pretty acute on that front. Many Android users have commented about how "bland" or "unchanging" the same 7 year old interface is, but there's always been 1 button, swipe and icon grid. It's so simple my 1 year old can literally navigate my iDevices and access netflix. She can't even speak yet. Android devices by contrast might have more flash or even customization but it's not as intuitive. Most devices that I've seen have 3 or 4 buttons in addition to the touch interface.
Sony needs to make a few tweaks, but I think they got more right with the UI.