We have mainly used marketo as a tool to contact current contacts to inform them of new products, training offerings, technology updates etc. When used with our major CRM we are able to track which contacts are interested in which topics and products.
Marketo being able to integrate with Salesforce.com is the main reason why we would renew. The two programs work well together and provide us with some great lead retrieval opportunities. Next time we review, an in-depth training would be needed in order to start using the program to its full potential.
Marketo has a well thought out lead scoring and campaign management process. The main interface is user friendly and the Marketo community is a great place to get insight from fellow users. The main problem is that companies using it aren't using it to its full potential, it doesn't help that it take a few days to hear back from a Marketo customer support if you can't figure something out.