Hmm... Seems I've been unlucky. I got a few duplicates after the sync, so I decided to clear the device to start off fresh. That sadly bricked it, and flashing it ends with the following error after a successful "erase", but unsuccessful copying of images:
So I guess I'll have to wait before I can test more.

To the questions that I had time to test: There is no landscape mode in the home screens, but most applications seem to have it implemented. The transition is flawless and quick.

The N950 does not seem to have a HDMI-port, only the 3.5mm jack which I suppose also delivers TV-out, although I haven't tested.

Edit: If someone else should encounter the same error, it seems like this is because the firmware version available online is older than the one shipped with the device. A downgrade is for some reason not allowed.