Microsoft has made Windows 10 Mobile Preview build 10512 available to Windows Insiders on the Fast update. That build has over 2,000 bug fixes compared to the last preview version, 10166, which was released over a month ago.
While Microsoft released a partial list of what's new and improved in Windows 10 Mobile build 10512, Windows Insider leader Gabriel Aul stated on Twitter that was just the tip of the iceberg:
"We've fixed more than 2K things since 10166, just listed a few top ones that Insiders reported."
That may seem like a lot of progress has been made, and it is, but Aul added in a follow-up message that the final version of Windows 10 Mobile is not just around the corner:
"No, we still have a way to go with Mobile before we're final."
Source: Gabriel Aul (Twitter)