I attended this event because I do some work with Salesforce and my company was willing to pay for it so it was basically a cheap vacation. I feel like it's largely a marketing event to showcase new features of Salesforce and showcase companies that have been successful using it and to that end it's effectively a big party.

There are useful aspect to it, though. It's an opportunity to network with people and other companies that use Salesforce and there are a lot of presentations on topics ranging from technical details of Salesforce to oceanography which can be useful for getting ideas on how to better utilize Salesforce. Salesforce has a large secondary market for applications built on it and Dreamforce is pretty good for companies with products in that market.