Watch the tutorials, depending on what email provider to which tutorial you watch:
http://optinrevolution.com/tutorials/
Are you planning to allow integration for not so popular autoresponders?
For example there are country specific autoresponders.
I got a plugin (InstaBuilder) where I can insert html code for sign up form from any autoresponder. It just detects form fields and everything works perfectly.
The Pro version can insert html code for any sign up form.
When pro will be available?
@atman1 next week. Go to http://www.optinrevolution.com and register to be notified.