Please note that when your available space gets around 2GBs left, the N7 often starts acting wonky, won't download other things, etc. This has been a documented issue' on the interwebs with the N7. (Not sure if all N7's have this issue but I've seen video and reports of a bunch of people having this problem.)
I, personally, have experienced this (on TWO UNITS) so basically I have to allot an extra 3GBs of space that can never be used to keep my N7 from freaking out... leaving my total usable storage, out of box- clean, to about 9-10GBs out of the 16GBs!
If you only surf the web and do a little emailing or IMing, that's more than enough space but God forbid you install an HD game, some magazines, books and a few videos?!? You're screwed. So I'd say, look at how you plan on using the device, add an extra few GBs for something unforeseeable and add it up. If its over 10GBs I would highly suggest you either look into OTG and/or cloud storage or wait for the 32GB version.
Personally, I would love to have the 32GB version. I want to store some of my content locally and not have to worry about not being able to install and play a game if its close to a gig in space or more. That's just rubbish.
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