As of my knowledge cutoff in September 2021, Ultrasurf's Chrome extension was considered reasonably safe, but like any browser extension, it comes with some caveats. While it does encrypt your browsing data, it's not a full-fledged VPN and only secures data transmitted within the Chrome browser. Also, the extension doesn't have the advanced features that you'd find in more robust VPN services. It's also worth noting that browser extensions can be more susceptible to leaks and attacks than standalone VPN apps.