In an unusual move for the company, Apple released new beta versions of its four operating systems in a row instead of all at once, as usual. First were iOS 10.1 and tvOS 10.0.1; then macOS 10.12.1. Today, to conclude the story, it was the turn of the watchOS 3.1 beta 3 (compilation 14S471).
The third test version of the update for the watch system does not bring anything new in relation to the previous ones besides bug fixes and performance improvements. WatchOS 3.1 by itself is also not an update that will bring new features, only improvements to the performance of the Apple Watch and bug fixes found in its previous version.
WatchOS 3.1 beta 3 is already available for installation through the Watch app on the respective iPhone, under "Software Update", in the "General" menu. You can also get the update from the Apple developer portal.