Re: Linux on mobile.
I replaced my N900 with an N9 after the USB port went and I got fed up swapping the battery every morning with the one in the external battery charger. It works brilliantly as a phone/messaging/email reader/web browser, and I especially love the "feeds" screen, which with a few free/open apps contains not only my twitter, facebook and RSS feeds, but also my upcoming calendar events. With Billboard I can also put a lof of information on the idle screen, such as time, current song, and IP address, which the N9 keeps displayed at all times with the low power OLED display. The 1GB of RAM over the 256MB of the N900 means it's much better at multi tasking and web browsing (the N900 couldn't use the web at all when I gave up on it).
Unfortunately I sorely miss the keyboard, that was one of the main reasons I hung onto the N900 for so long. The N9 can still ssh with X forwarding, but it's not nearly as useable without a physical keyboard. Swype helps with SMS messaging, but it's still a long way from a physical keyboard.
In summary the N9 is a fantastic phone, but the keyboard is what made the N900 great. I'd be more interested in Jolla if it wasn't so much bigger than the N9.