That is, I'd like to be able to change my mind about the vote, and only submit it when I click on the vote button at the end of the page.

I agree -- strange as it may sound.

If I end up at a node that I think is correct, I may signify my intention to upvote it by clicking on the ++ radio button, and continue by reading the replies. Sometimes I discover the node I originally upvoted is actually dead wrong -- in which case I may choose to change my vote to a downvote, or just decide not to vote on that node at all by navigating away from the page.

It doesn't happen often, but the flexibility would be very handy. Perhaps this should be user-configurable?