I now feel that Red Hat Enterprise 6 is okay (although not great)
Somewhat over a year ago I wrote about why I wasn't enthused about RHEL 6. Well, it's a year later and I've now installed and run a CentOS 6 machine for an important service that requires it, and as a result of that I have to take back some of my bad opinions from that entry. My new view is that overall RHEL 6 makes an okay Linux.
I haven't changed the details of my views from the first entry. The installer is still somewhat awkward and it remains an old-fashioned transitional system (although that has its benefits). But the whole thing is perfectly usable; both installing the machine and running it haven't run into any particular roadblocks and there's a decent amount to like.
I think that part of my shift is all of our work on our CentOS 7 machines has left me a lot more familiar with both NetworkManager and how to get rid of it (and why you want to do that). These days I know to do things like tick the 'connect automatically' button when configuring the system's network connections during install, for example (even though it should be the default).
Apart from that, well, I don't have much to say. I do think that we made the right decision for our new fileserver backends when we delayed them in order to use CentOS 7, even if this was part of a substantial delay. CentOS 6 is merely okay; CentOS 7 is decently nice. And yes, I prefer systemd to upstart.
(I could write a medium sized rant about all of the annoyances in the installer, but there's no point given that CentOS 7 is out and the CentOS 7 one is much better. The state of the art in Linux installers is moving forward, even if it's moving slowly. And anyways I'm spoiled by our customized Ubuntu install images, which preseed all of the unimportant or constant answers. Probably there is some way to do this with CentOS 6/7, but we don't install enough CentOS machines for me to spend the time to work out the answers and build customized install images and so on.)