Is there a way to import recipients into a list in Sprout Email? I have a couple of excel sheets with a list each of recipients for my e-mail campaigns. Is there a way to import that into Sprout Email? If not, I would really appreciate a pointer to where I could look to start hacking/building my own importer.
Sprout Email 2.x is not designed to be sending bulk email on it's own (September 2016). The feature is on our list to explore in future releases, and currently, Sprout Email can be used to manage sending bulk email via a third party mailer such as MailChimp or Campaign Monitor.

The current incarnation of "Recipient Lists" in Sprout Email is meant to be for very simple use cases where you may need to send Notification emails to a small list of people.  We will be revisiting the Recipient List feature to handle larger lists and integrations in the future.