Hi. A couple years back i suggested that plugin pages enable admins to vote for plugins to integrate into the WP core. Even Matt Mullenweg commented (inventor of WP, although i don't understand his comment)--
Anyway, I changed my mind, sort of. Even if you allowed voting only by logged in users, there's a better method:
integrate the MOST INSTALLED plugins to the core. Or at least, the ones which make sense as core features. (most installed, not most downloaded)
I suspect Matt may already be doin it ;)
But put the voting widget on each plugin page too (OR directly inside WP). Just more data to inform your choices.
(ps, i noticed several of the plugins i recommended in that old post have since been integrated into the core :)