Nature just published a survey of how scientists use social media:
The results confirm that ResearchGate is certainly well-known (see ‘Remarkable reach’, and full results online at go.nature.com/jvx7pl). More than 88% of scientists and engineers said that they were aware of it — slightly more than had heard of Google+ and Twitter — with little difference between countries. Just under half said that they visit regularly, putting the site second only to Google Scholar, and ahead of Facebook and LinkedIn. Almost 29% of regular visitors had signed up for a profile on ResearchGate in the past year.
Here is their graph for usage:
So a lot of people are “using” ResearchGate. But if you look into the details of how it’s being used, it’s basically LinkedIn for scientists. Something that people check and update because they feel like they should for professional reasons. But look at how people use these networks! It’s clear: if you want to discuss research and actually interact with other scientists, you should really be using Twitter.