9 months later the guy returned to Oracle. Always thought that spoke a little bit to the quality of OEL, especially after this profile from BI: https://www.businessinsider.com/wim-coekaerts-microsoft-open...
MSFT and Linux seem to be doing cool things right now, so I assume he returned to Oracle our of some love for the product, and not because he didn’t like what he saw at MSFT.
It was (as best as I can recall) perhaps a year or so after RHEL 6 dropped and, naturally, I was planning to use CentOS 6 for several new servers to be deployed (as most existing servers were running CentOS 5).
Unfortunately, while the 5.x releases of CentOS came out relatively quickly after RHEL, the first couple releases of 6.x were waaaaay behind! Around this same time, Oracle was pushing OEL over CentOS pretty hard , had recently announced their free public package repository (yum.oracle.com?) , and even had a "CentOS-to-OEL" shell script  you could run on existing CentOS hosts.
IIRC, it took them a couple months to get OEL 6.0 out the door, but it was still something like six months ahead of the CentOS 6.0 release! Fortunately, by 6.2 or so, CentOS had apparently got things figured out and were usually only two weeks or so behind RHEL. Yet, Oracle was still managing to push out minor releases and updates quicker. 
As these were public-facing servers I was about to deploy, the delay in releasing security updates was a big factor for me. I ended up deploying OEL6 on a number of new servers (although I never used ksplice, the UEK, or gave Oracle a single dollar) and continued to maintain them for several years without any issues that come to mind. I left $job right about a year ago and there were still a handful of those machines running then. Honestly, I would not be surprised to learn that some of them are still up and running today!
(EDIT: At least two of them are still up and running right now.)
(Side note: I had a 1U Sun server in one of our racks that hosted my personal web sites, e-mail, etc. From February 2013 until about three months ago -- when the hardware finally gave up the magic smoke -- it also ran Oracle Linux 6.)
(Disclaimer: I absolutely loathe Oracle and everything about them -- and ol' Larry -- but I still think that was the best decision at the time. Like many folks, I had high expections for CentOS once Red Hat took it under their wing but I've been quite disappointed.)
Disclaimer: I work at Red Hat.
Ubuntu 19.04 offers a radically more well-designed GUI and superior overall user experience compared to all Centos derivatives, and all previous versions of Ubuntu I've used. I've yet to meet a single soul genuinely using OEL7 full time on their primary machine. It's always Ubuntu these days :)
(I’m not a sysadmin so I don’t know if they were engaging in hyperbole or not.)