The Nokia N9 and the Nokia N900 had this integration feature for years. It's nice to have, but it was not and will never be a killer app.
There are no killer apps anymore
I know next to nothing about the N900 but killer apps need an ecosystem in which to exist. You can't just have one thing right and miss out on the other important stuff. Metro is an innovative UI that works really well. The marketplace has 50,000 apps. Who cares how many cores it has, the UI is responsive, properly written apps are fast to load and use.
Really, tell me how will the hardware manufacturers differentiate themselves when they ALL have to have the exact same OS and hardware specs, and they ALL have access to the same apps, etc.
This was pretty much my point. It's a problem MS have to get over. There's plenty they can do to achieve it. Manufacturers can use higher res, lower res screens (e.g. smaller, bigger). They can add keyboards. They can have better speakers, worse speakers, stereo speakers. They can have cool multi-colour polycarbonate shells. Or, they could do what Nokia is doing and write a few genuinely useful apps and parcel them with the device. I am of the opinion, as a developer, that if they can succeed with this, they've gone one over on Android (which is a royal pain to work with) and could easily get more market penetration than Apple.
Define properly conceived and integrated.
Yes, that was a rider to my main point so I didn't delve. I consider my WP7 device to be well conceived and properly integrated. It's a communications device and it covers most of the big communication services available to it and present them to me as one. I've not used the N900 but iPhone and Android certainly don't have it nailed as well as MS do.
Most consumers don't do "any amount of serious work". They read reddit, and update their status. They play games and compare scores. I'm not saying the tablet is right for everyone. I think some people will want a netbook (preferably with capactive touch screen, everything should have a capacitive touchscreen) and a cellphone. Some people might have a smartphone and a laptop, some might have every conceivable format of device (me for instance, that's likely me).