Creating your own custom HTML emails is clunky and time consuming. They should make that much easier.
1ShoppingCart has this great feature where you can create a list and the software will assign an email address to that list. You can give the email address to people and they can automatically sign up for that list. I'd LOVE to see Infusionsoft add something like that.
I would also like them to see them add an "ad tracking feature" (also available at 1ShoppingCart). You can create an ad-tracking link for a particular URL that shows how many times the link was clicked on and what purchases resulted from that link.
It's a big commitment to switch to Infusionsoft. It's well worth it, but you've got to be willing to put in the work to set it up and understand the concepts behind. So one needs to set aside the time and space to be able to do that.
To be honest, we've invested so much time in setting up Infusionsoft, I"m not willing to start over with a new software and it does 90% of what I want so I'm happy with the product. Plus their customer service is stellar and I really appreciate that.