I am not an employee, but here are my two cents. IBM is, as far a I can tell, the best example of a "mixed bag" in tech. I have heard both great and terrible things about IBM from customers, employees, developers on Open Source projects, etc. They are a huge organization, and one that seems more divided than many.
It may be more useful to view IBM as a collection of fiefdoms rather than a single, focused, entity. Yes, the money all goes into one pot at the end of the day, but there's large variance across organizations within IBM.
That said, from what I can tell OSS that goes into the IBM machine doesn't usually come out the other side improved. I worry for the health of CentOS/RHEL/Fedora under IBM's leadership. My desktop and server OS of choice, with a few brief forays into other territories along the way, has been from Red Hat for 23 years. I'd hate to lose Fedora or CentOS, or see them stagnate. Red Hat has been among the most steadfast in their support of Open Source software, as well...so, there's a real risk of the kernel, Gnome, and other OSS core infrastructure suffering, because Red Hat is a major contributor to those projects.
I don't think it'll be sudden. It usually takes years for projects to become clearly worse for having come under IBM's purview. Red Hat is large itself, and will probably take years to be fully assimilated and homogenized into IBM's lukewarm culture of mere competence with regard to their Open Source contributions.