It is a very user-friendly solution. I'm mainly working on Design Studio, which is useful for companies in tracking repeat users. The progressive proofing is also useful. It is not available in other solutions.

The most valuable feature is the scoring.

The most valuable features are the Marketo emails, both sending and tracking. 

Marketo provides detailed tracking. For example, it shows you who has clicked on which link, who has opened the email, and when it was received. 

They are improving it and have launched a new version, called Micro Sky, and it seems very good.

The smart campaign looks quite interesting and useful. My experience is in sales, though we use Marketo for marketing it has more strength for sales. They have a very good lead force system when somebody views our website or clicks on something, I notice a strong interest. I am able to understand what is the customer is looking for and what is the feature, or function that they care about. This solution gives me a qualified lead, it will drive your sales even faster. This is the beauty I found out about Marketo.

The main feature of Marketo is sending out emails, so that would be the most valuable feature.