What about localization ?

This plugin was full internationalized because use localized string from WordPress core.

What about spam? Will I get a lot from the contact form?

If you have Akismet installed on your blog, you shouldn’t get much spam.
All the messages people send to you through the contact form will be filtered through Akismet.

Anyone can put whatever they want in the name and email boxes. How can I know who’s really sending the message?

If a logged member of your site sends you a message, the end of the email will let you know that the message was sent by a verified user.
Otherwise, you can’t trust anything… just like a blog comment.

Anonymity is both a curse and a blessing :)

My blog has multiple authors. Who gets the email?

By default, the email is sent to the author of the post with the contact form in it. So each author on your blog can have his or her own contact form.

In the contact form shortcode, you can specify what email address(es) messages should be sent to with the to parameter.

Great! But how will my visitors know who they’re sending a message to?

Just make the title of your post “Contact Mary” or put “Hey, drop John a line with the form below” in the body of your post.