Has anyone heard of the Enneagram Personality Test, and if so, what has your experience been? Researching assessments used for personal development, organizational development, selection and talent management and have came across some new tools I haven't found before.  Made me think that I am very sheltered in information and thought I would reach out and find out what experience others have in effective options. Looking for options for midlevel company ($500M) multi-demographic US based company.

Lots of people use it - especially people who have more of a data background.  I like assessments that have rich research bases that have shown validity across geographies and demographics etc.  Very few meet that criteria. Really depends on what you are trying to do.  if it is to just drive team building and some get to know you things tried and true assessments like Myers Briggs and DiSC are good, also things like Belbin. There is a company called Cloverleaf that is a platform for bringing many different assessments together and delivering through platforms like outlook and teams to help people better approach others --i personally like Hermann Brain Dominance instrument,  (HBDI) https://www.thinkherrmann.com/hbdi 
because it is one of the most researched and validated instruments worldwide.  We use it to learn about different thinking styles and improve communications --but it can be used by leadership teams, working teams and more importantly they have a lot of support for applications in DEI&B.

I have heard of it - and your post was the impetus to check it out - https://en.wikipedia.org/wiki/Enneagram_of_Personality. Appears to have been discredited. Reminds me of hand-writing analysis, more common in some countries and not at all a useful selection tool or predictor. Beware of 'shiny new things' (a phrase I think used by Allan Church, formerly VP, Talent at Pepsico) that purport to predict performance or potential. 

I'd recommend reviewing a recent meta-analysis of the best predictors of performance - the top list tends to include cognitive ability and structured interviewing. Once you have a good sense of the typical validity of different types of predictors or tools, you can use that to direct what you are looking for. If you are looking to assess personality, then most organisational psychologists would advice using the most well-known psychometrics, like Hogan's HPI and HDS, SHL's OPQ, Saville's Wave and the like.