4.3" screen if it's a modified version of the HTC Passion or the HD2, as has been guessed in numerous reports, e.g.,

http://www.washingtonpost.com/wp-dyn...121301694.html

and

http://www.slashgear.com/google-nexu...phone-1265839/

Hence, say I: "Larger screen. Very interested."

For coding you might need a hardware keyboard, but voice-to-text, as is rumored, will be much faster for most users when they can use it. For those times when you can't appropriately speak aloud, a good screen-based keyboard ought to be sufficient to fill the gap.