Interspire is absolutely brilliant. Aweber is all hype and that 99% deliverability is all BS.

Just set up a new domain to send mail from so that its black list status is clear. The install domainkeys and a SPF record on this server and your mail will end up in the inbox without any issues.

Process all hard bounces daily and incase your domain does end up in any black list, wrote to them and they will usually clear your domain.

Domainkeys and spf are the 2 things that most self hosted emailer neglect and hence have poor deliverability. I mean think about it, there is nothing special about awebers mail server and your own.

Only aweber has domainkeys and spf which you don't