Events builder - you need HTML / CSS knowledge. (May as well use Dreamweaver)
Need to use HTML / CSS to create Landing pages.
There is no delete function within the nurture campaign - if you make a mistake you need to start over.
Lack of information when analyzing an event - i.e. You can't see who has specifically declined an event in comparison to who just hasn't seen the email.
When testing an email - the test email doesn't always come through.
The HTML of the email temples causes most spam filters to block your emails (unless you know how to hard code you can't fix this).
Look at Mail Chimp. Much cheaper, no coding skills needed, social media integration and spam testing all included. (None of this is included in SF)