So download your aweber list csv and then just upload it to mailchimp.
The only problem is that autoresponders don't seem to work for old users unless you do a dirty hack
Does the bulk import send everyone a resubscribe message? I've got a very small list (sub 100 people) of customers and prospects that I meet with IRL, and I don't want to annoy them by asking them to subscribe again to a list they've already subscribed to.
No, bulk importing does not send a resubscribe message. MailChimp assumes that if you have access to the address list, then you have permission to send.