Does SlideIn combined with eNewsletter do everything...

I'm thinking of combining SlideIn to add to my user/subscriber list, and eNewsletter to send newsletters, etc. I currently use AWeber, but from looking at these two plugins it seems to me there is really no reason for using an autoresponder company...it looks like these two combined do it ALL.

Two questions:
1. Am I missing something? Is there something AWeber does that would make me want to keep it?
2. Can I import the list(s) I have from AWeber into my site's users/subscriber list(s)?