I realise I'm about 15 months late, but I have the same problem as the OP and stumbled upon this thread while searching for an answer. I use Evernote on 2 phones (personal, work), 3 laptops (personal + 2 work) and 2 tablets (both personal). I'd really prefer work devices to use one default notebook, personal devices to another, and the tablets to a household notebook.
The suggestion of using multiple accounts (even if they were free) seems excessive. That makes it significantly more complicated to achieve a per-device default notebook. Now I'd need to manage multiple passwords, login emails, etc, and which account is the one which actually gets billed, etc. Evernote is meant to simplify my life!
Finding notes is never a problem, as there's the "All notes" view (which can show you everything created recently at a glance), and the search is pretty stellar.
But getting notes into the right notebook in the first place is an extra conscious step which Evernote could solve so easily for me if only it had a per-device default notebook. The reason I use and love Evernote is that it takes the tedious labor of managing documents. Having to manually file each note is plain tedious.
Yes! This implementation would suit me perfectly.
Don't explicitly prompt users to nominate a default notebook per-device. It's obviously a power-user feature. Just provide a preference for it in the menu.
Even better would be something like the proposed action rules stuff [https://discussion.evernote.com/topic/22086-rules-engine/] where you can specify a set of rules to define which notebook a note will go into, and then you could base it on all sorts of things including the device you're on. I imagine that's way too advanced to ever fly in Evernote though.