Google ads service

DoubleClick suits better to businesses which have considerably bigger advertising needs. Think about a business which runs ads across multiple search engines and network, for such businesses it would be difficult to manage campaigns individually. They will need to go to AdWords to manage ads on Google inventory, and to BingAds to manage ads with Bing, and so.

DoubleClick gives them a consolidated dashboard where they can manage everything from single platform.

When it comes to features for ads, you usually have almost all features with AdWords as well.

If you are an agency or a business having advanced management and reporting requirements for your consolidated digital marketing efforts, or you are running ads across multiple search engines, you can apply for DoubleClick. However, if you want to use DoubleClick for rather small business, it won't be a good fit as it will be adding overhead to your overall advertising spends. If you think your needs are comprehensive enough to justify the charges for doubleclick, it's always great to use it.

My two cents.

EDIT -

So are there any marketers using it?

Don't say ANY, there are MANY MANY marketers using it . As I said, DoubleClicks is a robust platform.