What do you like best?
The breadth of the platform. It has all the features you want, need, and didn't even know it had.
Where it lacks in polish, it makes up for in power - no question.
While some might not like how customizable the ENTIRE platform is, it gives you the tools you need to do what you want. If you're expecting to hop in, map some fields, and get automating - you might be a little disappointed. If you're looking to build your dream digital strategy and not be limited by pre-defined fields and automation flows, this is your tool.
If you don't have a team with an Art Director that is comfortable with some HTML, you will likely need a consultant (if you're very particular about email and page design).
What do you dislike?
It's a little clunky and, if I were to nitpick, I could write several pages of change requests for the interface. You enter the platform blind, as nothing is pre-configured - which is a blessing and a curse. While you are not held back by limited automation flows, custom fields, etc, the number of options can be crippling. Also, the WYSIWYG tools are just that and you're going to have to play with them for a while. If you're capable of ripping out some of their code and starting fresh, it'll do what you need.
Also worth noting - in my detailed feature review, most features were knocked a point or two for the interface. It really does have everything you'll probably ever need and it'll help in saving time. While it might not be the best or most polished - it is 100% worth it for the price, especially compared to nearly every other end-to-end service such as this.
Recommendations to others considering the product
If you're a massive enterprise, it probably isn't the right solution. If you're a small/medium sized business or a startup that needs to stay in communication with many customers and prospects and would like to be able to edit just about everything they'll see from web to email, this is for you.
What business problems are you solving with the product? What benefits have you realized?
Marketing automation - drip campaigns, newsletters, dynamic content, lead scoring, everything you'd expect. It's taken some time to get everything up and running (we have a small team), but it's pretty exciting to see it start paying off. I cannot say we have truly benefited yet, but we see the potential and are starting to see the payoff.