Much of the reporting and analytics. MOST of the reporting and analytics actually.

There's another hidden pitfall: If you build up your list and want to move to Aweber in the future, you can't just transfer your list. Everyone HAS to re-opt-in... which means you'll have to ask them to.

Conventional wisdom is that if you are forced to go that route, if you're able to secure a 25% retention rate you're doing pretty good.

Think long and hard about the long term repercussions of not setting it up right the first time.