I like that I can create multiple variations of the same email, allowing me to see which ones perform better. We've been using this for about 1 year now and haven't had any issues with it yet! There's nothing specific we dislike as much as we would have liked there to be. The amount of time saved is well worth the price of admission. If you don't already use Mailchimp or another similar service make sure you do before you get too attached to one tool because they all tend to evolve over time…