Microsoft has published an update on its Windows Insider Program, which allows you to experience the latest Windows 10 preview builds once out, revealing that as of December more than 1.5 million registered users are participating in it. Roughly 450k of those are what Microsoft considers “highly active”, meaning they are using the latest build of Windows 10 on a daily basis, “putting it through its paces,” as the company says.

“We continue to be humbled by all the feedback we’re getting from the Windows Insider Program,” the software giant said in its blog post.

Microsoft also notes that Windows Insiders are using Windows 10 preview builds more actively than those in preview/beta programs for any prior release of the operating system. The company is excited to see this especially because it’s giving them a chance to fix all the rough edges and bugs.

As an example, Microsoft cited a bug that allowed the OneDrive icon in File Explorer to be replaced by the Outlook icon, something the company says “would have been really tricky to catch with test automation or by other means.” While this is a fairly innocuous problem, the company says it has fixed almost 1,300 other bugs reported by Insiders, and has also made changes to the UX or features based on users’ suggestions.

The update comes just a week after Microsoft announced that it is holding a special Windows 10 event in Redmond, Washington on January 21st.