The updated app adds things like admin privileges, advanced search, and the ability to order the ‘home stream’ (Currents, get it?) by relevance or time.
Reports say that existing Google+ URLS will now automatically redirect to Currents URLs, but that Google intends to keep this strictly for business use. It merely now adds to Google’s heaving, confusing number of apps and services. It doesn’t appear that Currents is going to keep Slack or Microsoft Teams up at night, either. But you never know.