Infusionsoft has robust capability as an email marketing platform. You can get as detailed as you want with categories and tags for future segment marketing.
The ability to create "if this, then that" type scenarios with email marketing allows users to laser target their sales funnels for specific audiences.
The new Snap app allows you to take a picture of business cards with your smartphone and then upload directly to Infusionsoft (the information is reviewed by live people to ensure it imports right). This makes your lead gen efforts instant and almost effortless.
Infusionsoft is extremely strict with SPAM. This isn't a "done poorly" feature by any means, but if you want to market to existing email lists that are old, or maybe weren't obtained with opt-in functionality, Infusionsoft may not work well for you.
Because of how robust Infusionsoft is (again, not a negative in and of itself), it can be overwhelming and time intensive for the average user or business owner to implement.