I want to run a Javascript console on top of V8. How do I do this?
If you're planning to embed V8, then by all means build it and play with "d8".
If on the other hand, you do not plan to extend V8 or treat it as optional, then just use Node.JS. Don't bother with pure V8.
Node.js has truly rich I/O, extensions, libraries (like Perl CPAN, Python Eggs, Ruby Gems), and community.