Larry, It is officially still in Beta and has been in beta since agent v131. It has been in the field since Nov 2017. You might ask, 'Why so long'? I don't have a good answer however I would encourage you to utilize it as you need. This 'new' feature has had lots of real world usage and testing.
I have OneAgents running in non-root mode successfully at several customers without any issues. However, I remember there were some issues fixed in OneAgent 1.147 and 1.153 about non-root mode.
Maybe @Bartosz G. will give you an answer about the beta status.
As noted by Joseph and Julius, the solution is still in beta phase. We target end of Q1 as a GA release. Before that happens we need to improve several smaller technicalities a bit, most importantly in the areas of the internal test coverage. That is required to meet our own high quality standards.
All that being said, it is perfectly fine to use it in production. We provide official, regular support for all our beta features, including the non-privileged mode for OneAgent in Linux. From the usage analytics data we know that it is currently deployed on several thousands of Linux hosts maintained by our customers and is working perfectly fine there.