In addition to the current events, please do the following:
1. add a "NOT" modifier
In front of every event you should have the negative option. Example:
If user NOT opened broadcast email -> send follow up.
If user NOT clicked link ...
2. add event "user replied to email"
3. Allow multiple actions
Example: If user clicked link -> send follow up + add tag + add subscription
This would be the most important.
Please also take a look at your (indirect) competitor: http://www.activecampaign.com/automation/
I think there are some nice automatic action features you could adopt. Doing this would give you a huge advantage since no other self-hosted autoresponder software has this (it's so important to me that I just googled literally 2 hours, and I'm sure as hell not the only one).